Envision Math Grade 8 Volume 1 Student Edition Solutions Chapter 1 Real Number Exercise 1.2

Envision Math Grade 8 Volume 1 Student Edition Solutions Chapter 1 Real Number Exercise 1.2

Envision Math Grade 8 Volume 1 Chapter 1 Exercise 1.2 Real Number Solutions

Page 13 Exercise 1 Answer

Given that, Sofia wrote a decimal as a fraction. Her classmate Nora says that her method and answer are not correct. Sofia disagrees and says that this is the method she learned.

We need to construct Arguments whether Nora or Sofia is correct or not.

The given decimal is 0.12112111211112…

Here, Sofia wrote this decimal as a fraction.

But it cannot be represented as a fraction since the given number is an irrational number.

Only terminating and repeating decimals can be represented as a fraction.

Here, the decimal is not terminating and it is not repeating. Thus, it cannot be represented as a fraction.

Nora’s Argument is correct. The given number cannot be represented as a fraction since it is an irrational number.

 

Page 13 Exercise 2 Answer

We need to write another nonterminating decimal number that can not be written as a fraction.

Only terminating and repeating decimals can be represented as a fraction.

If the decimal is not terminating and it is not repeating, it cannot be represented as a fraction.

Some of the examples of nonterminating decimal numbers that can not be written as fractions are,

0.15267389…

0.3512649…

0.125112511125…

Another nonterminating decimal number that can not be written as a fraction is 0.125112511125…

Envision Math Grade 8 Volume 1 Student Edition Solutions Chapter 1 Real Number Exercise 1.2

Page 13 Exercise 1 Answer

We need to find whether 0.12112111211112… is a rational number or not.

Irrational numbers cannot be represented as a fraction.

Irrational numbers are non-terminating and non-repeating in nature.

Only terminating and repeating decimals can be represented as a fraction.

Rational numbers are terminating and repeating in nature.

Here, the given number 0.12112111211112… is non-terminating and non-repeating in nature.

Hence, it is an irrational number.

The given decimal 0.12112111211112… is an irrational number.

Envision Math Grade 8 Student Edition Exercise 1.2 Real Numbers Answers

Envision Math Grade 8 Volume 1 Student Edition Solutions Chapter 1 Real Number Exercise 1.2 Page 14 Question 1 Answer

We need to explain how an irrational number is different from a rational number.

Irrational numbers cannot be represented as a fraction.

Irrational numbers are non-terminating and non-repeating in nature.

Only terminating and repeating decimals can be represented as a fraction.

Rational numbers are terminating and repeating in nature.

Only rational numbers can be represented as a fraction while irrational numbers cannot.

Terminating and repeating decimals are known as rational numbers while non-terminating and non-repeating decimals are known as irrational numbers.

Page 14 Exercise 1 Answer

We need to classify the below numbers as rational or irrational.

The numbers are

π

3.565565556…

0.04053661…

-17

0.76

3.275

Irrational numbers cannot be represented as a fraction. Irrational numbers are non-terminating and non-repeating in nature.

Only terminating and repeating decimals can be represented as a fraction.

Rational numbers are terminating and repeating in nature. Only rational numbers can be represented as a fraction while irrational numbers cannot.

Rational numbers are:

π=3.14159

−17

0.76

3.275

Irrational numbers are:

3.565565556…

0.04053661…
Real Numbers Page 14 Exercise 1 Answer

 

Page 15 Exercise 2 Answer

We need to classify the below numbers as rational or irrational.
\(\frac{2}{3}\),√25,−0.75,√2,7,548,123

Irrational numbers cannot be represented as a fraction. Irrational numbers are non-terminating and non-repeating in nature.

Only terminating and repeating decimals can be represented as a fraction.

Rational numbers are terminating and repeating in nature. Only rational numbers can be represented as a fraction while irrational numbers cannot.

Rational numbers are:

\(\frac{2}{3}\),√25,−0.75,7,548,123

Irrational number is: √2

Rational numbers: \(\frac{2}{3}\),√25,−0.75,7,548,123

Irrational numbers: √2

Envision Math Grade 8 Volume 1 Student Edition Solutions Chapter 1 Real Number Exercise 1.2 Page 14 Exercise 1 Answer

Given that, Jen classifies the number 4.567 as irrational because it does not repeat. We need to construct arguments whether Jen is correct or not.

Irrational numbers cannot be represented as a fraction.

Irrational numbers are non-terminating and non-repeating in nature.

Only terminating and repeating decimals can be represented as a fraction.

Rational numbers are terminating and repeating in nature.

Only rational numbers can be represented as a fraction while irrational numbers cannot.

The number 4.567 is terminating in nature.

Hence, the given number is a rational number.

Jen’s argument is incorrect.

 

Page 16 Exercise 1 Answer

We need to describe the difference between the irrational number and a rational number.

Irrational numbers cannot be represented as a fraction.

Irrational numbers are non-terminating and non-repeating in nature.

Only terminating and repeating decimals can be represented as a fraction.

Rational numbers are terminating and repeating in nature.

Only rational numbers can be represented as a fraction while irrational numbers cannot.

Terminating and repeating decimals are known as rational numbers while non-terminating and non-repeating decimals are known as irrational numbers.

 

Page 16 Exercise 3 Answer

We need to explain whether a number could ever be both rational and irrational.

Irrational numbers cannot be represented as a fraction.

Irrational numbers are non-terminating and non-repeating in nature.

Only terminating and repeating decimals can be represented as a fraction.

Rational numbers are terminating and repeating in nature.

Only rational numbers can be represented as a fraction while irrational numbers cannot.

A number could never be both rational and irrational. It has to be one or the other.

Real Number Solutions Grade 8 Exercise 1.2 Envision Math

Envision Math Grade 8 Volume 1 Student Edition Solutions Chapter 1 Real Number Exercise 1.2 Page 16 Exercise 4 Answer

We need to explain whether the number 65.4349224… is rational or irrational.

Irrational numbers cannot be represented as a fraction.

Irrational numbers are non-terminating and non-repeating in nature.

Only terminating and repeating decimals can be represented as a fraction.

Rational numbers are terminating and repeating in nature.

Only rational numbers can be represented as a fraction while irrational numbers cannot.

The given number 65.4349224… is non-terminating and non-repeating in nature.

Hence, it is an irrational number.

The given number 65.4349224… is an irrational number.

 

Page 16 Exercise 5 Answer

We need to explain whether the number√2500 is rational or irrational.

Irrational numbers cannot be represented as a fraction.

Irrational numbers are non-terminating and non-repeating in nature.

Only terminating and repeating decimals can be represented as a fraction.

Rational numbers are terminating and repeating in nature.

Only rational numbers can be represented as a fraction while irrational numbers cannot.

The given number √2500 = 50 is a perfect square number.

Hence, it is an rational number.

The given number √2500 is an rational number.

Envision Math Grade 8 Chapter 1 Exercise 1.2 Solutions

Envision Math Grade 8 Volume 1 Student Edition Solutions Chapter 1 Real Number Exercise 1.2 Page 16 Exercise 6 Answer

We need to classify each number as rational or irrational.
The numbers given are,

\(4.2 \overline{7}\)

0.375

0.232342345…

\(\sqrt{62}\) \(-\frac{13}{1}\)

Irrational numbers cannot be represented as a fraction.

Irrational numbers are non-terminating and non-repeating in nature.

Only terminating and repeating decimals can be represented as a fraction.

Rational numbers are terminating and repeating in nature.

Only rational numbers can be represented as a fraction while irrational numbers cannot.

Rational numbers are:

\(4.2 \overline{7}\)

0.375

\(-\frac{13}{1}\)

Irrational numbers are:

0.232342345…

\(\sqrt{62}\)

Rational numbers: \(4.2 \overline{7}, 0.375, \frac{-13}{1}\)

Irrational numbers: 0.232342345…, \(\sqrt{62}\)

 

Page 17 Exercise 7 Answer

We need to explain whether the number5.787787778… is rational or irrational.

Irrational numbers cannot be represented as a fraction.

Irrational numbers are non-terminating and non-repeating in nature.

Only terminating and repeating decimals can be represented as a fraction.

Rational numbers are terminating and repeating in nature.

Only rational numbers can be represented as a fraction while irrational numbers cannot.

The given number 5.787787778… is non-terminating and non-repeating in nature.

Hence, it is an irrational number.

The given number 5.787787778… is an irrational number.

Envision Math 8th Grade Exercise 1.2 Step-By-Step Real Number Solution

Envision Math Grade 8 Volume 1 Student Edition Solutions Chapter 1 Real Number Exercise 1.2 Page 17 Exercise 8 Answer

We need to explain whether the number √42 is rational or irrational.

Irrational numbers cannot be represented as a fraction.

Irrational numbers are non-terminating and non-repeating in nature.

Only terminating and repeating decimals can be represented as a fraction.

Rational numbers are terminating and repeating in nature.

Only rational numbers can be represented as a fraction while irrational numbers cannot.

The given number √42 is not the square root of a perfect square number.

Hence, it is an irrational number.

The given number √42 is an irrational number.

 

Page 17 Exercise 10 Answer

We need to circle the irrational number in the given list:
Real Numbers Page 17 Exercise 10 Answer Image 1

Irrational numbers cannot be represented as a fraction.

Irrational numbers are non-terminating and non-repeating in nature.

Only terminating and repeating decimals can be represented as a fraction.

Rational numbers are terminating and repeating in nature.

Only rational numbers can be represented as a fraction while irrational numbers cannot.

\(7.2 \overline{7}=7.27777 \ldots\)

\(\frac{5}{9}\) \(\sqrt{196}=14\)

These are rational numbers since it is repeating and terminating in nature.

The number √15 is irrational since 15 is not a perfect square number.

The irrational number is circled below,
Real Numbers Page 17 Exercise 10 Answer Image 2

 

 

Page 17 Exercise 11 Part (a) Answer

The given numbers are 5.737737773…,26,√45 \(\frac{-3}{2}\),0,9

We need to find the rational numbers in it.

Irrational numbers cannot be represented as a fraction.

Irrational numbers are non-terminating and non-repeating in nature.

Only terminating and repeating decimals can be represented as a fraction.

Rational numbers are terminating and repeating in nature.

Only rational numbers can be represented as a fraction while irrational numbers cannot.

The rational numbers are 26,\(\frac{-3}{2}\),0,9

The rational numbers in the list will be 26,\(\frac{-3}{2}\),0,9

 

Envision Math Grade 8 Volume 1 Student Edition Solutions Chapter 1 Real Number Exercise 1.2 Page 18 Exercise 14 Answer

We need to check whether the decimal form of \(\frac{13}{3}\) is a rational number or not.

Irrational numbers cannot be represented as a fraction.

Irrational numbers are non-terminating and non-repeating in nature.

Only terminating and repeating decimals can be represented as a fraction.

Rational numbers are terminating and repeating in nature.

Only rational numbers can be represented as a fraction while irrational numbers cannot.

The decimal form of the given number is,

\(\frac{13}{3}=4.33333 \ldots\)

The given number is non-terminating and repeating in nature.

Thus, the given number is rational.

The decimal form of \(\frac{13}{3}\) is rational.

How To Solve Exercise 1.2 Real Numbers In Envision Math Grade 8

Page 18 Exercise 18 Answer

We need to find the rational numbers among the following:

1. 1.111111…

2. 1.567…

3. 1.101101110…

Irrational numbers cannot be represented as a fraction.

Irrational numbers are non-terminating and non-repeating in nature.

Only terminating and repeating decimals can be represented as a fraction.

Rational numbers are terminating and repeating in nature.

Only rational numbers can be represented as a fraction while irrational numbers cannot.

1. 1.111111…

This number is rational since it is repeating in nature.

2. 1.567…

This number is irrational since it is non-repeating and non-terminating in nature.

3. 1.101101110…

This number is irrational since it is non-repeating and non-terminating in nature.

The correct option is (E) I only.

Only 1. 1.111111… is rational others are irrational.

Envision Math Grade 8 Exercise 1.2 Practice Problems

Envision Math Grade 8 Volume 1 Student Edition Solutions Chapter 1 Real Number Exercise 1.2 Page 18 Exercise 19 Answer

We need to classify the given numbers as rational or irrational.

The numbers are

\(\frac{8}{5}, \pi, 0, \sqrt{1}, 4.46466 \ldots,-6, \sqrt{2}\)

The given numbers are \(\frac{8}{5}, \pi, 0, \sqrt{1}, 4.46466 \ldots,-6, \sqrt{2}\)

Irrational numbers cannot be represented as a fraction.

Irrational numbers are non-terminating and non-repeating in nature.

Only terminating and repeating decimals can be represented as a fraction.

Rational numbers are terminating and repeating in nature.

Only rational numbers can be represendted as a fraction while irrational numbers cannot.

\(\frac{8}{5}, \pi=\frac{22}{7}, 0, \sqrt{1},-6\) are rationa since it is terminating in nature.

4.46466…., √2 are irrational since it is nonterminating and the roots are not of the perfect squares.
Real Numbers Page 18 Exercise 19 Answer

 

 

Envision Math Grade 8 Volume 1 Student Edition Solutions Chapter 1 Real Number Exercise 1.1

Envision Math Grade 8 Volume 1 Student Edition Solutions Chapter 1 Real Number Exercise 1.1

Page 2 Question 1 Answer

A real number would be any number which can be discovered in the actual world. Numbers can be found all around us.

Natural numbers are being used to count objects.

Rational numbers are being used to portray fractions.

Irrational numbers are being used to calculate the square root of an amount.

Integers are used to measure temperature, among other things.

These various types of numbers combine form a gathering of real numbers.

Except complex numbers, everything come under real numbers.

It is denoted by R and it is the union of both rational and irrational numbers and it is represented by \(R=Q \cup \bar{Q}\)

Envision Math Grade 8 Volume 1 Student Edition Solutions Chapter 1 Real Number Exercise 1.1

Page 2 Question 2 Answer

A real number would be any number which can be discovered in the actual world. Numbers can be found all around us.

Natural numbers are being used to count objects.

Rational numbers are being used to portray fractions.

Irrational numbers are being used to calculate the square root of an amount.

Integers are used to measure temperature, among other things.

These various types of numbers combine to form a gathering of real numbers.

Real numbers are used in many places to solve problems. For example, it is used to portray fractions, determine square roots, measure temperature, and for counting things, etc.

 

Envision Math Grade 8 Volume 1 Student Edition Solutions Chapter 1 Real Number Exercise 1.1 Page 5 Exercise 1 Answer

We know that the addition of zeroes at the end of a decimal number doesn’t change its value.

A number that has a finite number of decimals in it can also be represented by adding repeating zeroes at the end of it.

Even though we add repeating zeroes, the number of decimals present in the given number is finite.

The given number terminates at this point. Thus, it is a terminating decimal.

A finite number of decimals can also be represented in the form of repeating zeroes at the end.
For example,

12.2750000 or 12.275

15.840000 or 15.84

These are some of the examples of terminating decimal which has repeating zeros in it.

A terminating decimal is a decimal that ends in repeating zeros.

 

Page 5 Exercise 2 Answer

We know that the addition of zeroes at the end of a decimal number doesn’t change its value.

But if the decimal gets repeated again and again, the loop goes endlessly and the digits repeat forever.

A number that has an infinite number of decimals in it is termed to be the repeating decimals.

A repeating decimal doesn’t terminate at any point. The decimal will be infinite.

For example,

15.57 or 15.575757….

\(19.75 \overline{4} \text { or } 19.754444444 \ldots\)

These are some of the examples of repeating decimal which has repeating digits in it.

A repeating decimal is a decimal in which a digit or digits repeat endlessly.

 

Envision Math Grade 8 Volume 1 Student Edition Solutions Chapter 1 Real Number Exercise 1.1 Page 5 Exercise 4 Answer

We can write any number as a fraction.

A fraction can be used to describe the part of the things.

It is described as a part of a whole or a part of a set.

The division of any number is said to be the fraction.

For example, if we are going to eat half of the eight eggs we have, it is represented as,

\(\frac{1}{2} \times 8=4\)

A fraction is a number that can be describe a part of a whole, a part of a set, a location on a number line, or a division of whole numbers.

 

Page 5 Exercise 7 Answer

Given decimal is 7.0001

We need to determine whether the given decimal is terminating or repeating.

The given number is 7.0001

It can also be written as 7.00010000000000000000…

Since they both represent the same.

This is because the addition of zeroes at the end of a decimal number doesn’t change its value.

A number that has a finite number of decimals in it can also be represented by adding repeating zeroes at the end of it.

Even though we add repeating zeroes, the number of decimals present in the given number is finite. i.e., .0001.

The given number terminates at this point. Thus, it is a terminating decimal.

The given number 7.0001 is a terminating decimal.

 

Page 5 Exercise 9 Answer

Given decimal is \(1.1 \overline{7} 8\)

We need to determine whether the given decimal is terminating or repeating.

The given number is \(1.1 \overline{7} 8\)

A number that has a finite number of decimals in it can also be represented by adding repeating zeroes at the end of it.

Even though we add repeating zeroes, the number of decimals present in the given number is finite.

If the number of decimals is infinite and the number gets repeated again and again, it is referred as repeating decimal.

The given number doesn’t terminate at any point as it has an infinite number of decimals.

The number 178 gets repeated again and again.

The given number can also be represented as 1.178178178…

Thus, it is a repeating decimal.

The given number \(1.1 \overline{7} 8\) is a repeating decimal.

 

Envision Math Grade 8 Volume 1 Student Edition Solutions Chapter 1 Real Number Exercise 1.1 Page 5 Exercise 10 Answer

Given decimal is −4.03479

We need to determine whether the given decimal is terminating or repeating.

The given number is −4.03479

A number that has a finite number of decimals in it can also be represented by adding repeating zeroes at the end of it.

Even though we add repeating zeroes, the number of decimals present in the given number is finite.

The given number terminates at this point as it has a finite number of decimals. Thus, it is a terminating decimal.

The given number -4.03479 is a terminating decimal.

 

Page 5 Exercise 11 Answer

We need to find the product of 2.2

Performing multiplication on the given numbers, we get,

2.2 = 2 x 2
= 4

Thus, the product will be 4.

The product of 2.2 = 4

 

Page 5 Exercise 12 Answer

We need to find the product of -5 . -5

In multiplication, the product of two positive numbers or two negative numbers will result in a positive number.

The product of a negative and a positive number will result in a negative number.

Performing multiplication on the given numbers, we get,

(−5)⋅(−5)=5×5

=25

Thus, the product will be 25.

The product of −5 ⋅ −5 = 25

 

Envision Math Grade 8 Volume 1 Student Edition Solutions Chapter 1 Real Number Exercise 1.1 Page 5 Exercise 13 Answer

We need to find the product of 7⋅7

In multiplication, the product of two positive numbers or two negative numbers will result in a positive number.

The product of a negative and a positive number will result in a negative number.

Performing multiplication on the given numbers, we get,

7 ⋅ 7 = 7 × 7

= 49

Thus, the product will be 49

The product of 7⋅7 = 49

 

Page 5 Exercise 14 Answer

We need to find the product of −6⋅(−6)⋅(−6)

In multiplication, the product of two positive numbers or two negative numbers will result in a positive number.

The product of a negative and a positive number will result in a negative number.

Performing multiplication on the given numbers, we get,
Real Numbers Page 5 Exercise 14 Answer


Thus, the product will be −216

The product of −6⋅(−6)⋅(−6) = −216

 

Envision Math Grade 8 Volume 1 Student Edition Solutions Chapter 1 Real Number Exercise 1.1 Page 5 Exercise 16 Answer

We need to find the product of −9⋅(−9)⋅(−9)

In multiplication, the product of two positive numbers or two negative numbers will result in a positive number.

The product of a negative and a positive number will result in a negative number.

Performing multiplication on the given numbers, we get,
Real Numbers Page 5 Exercise 16 Answer

The product of −9⋅(−9)⋅(−9) = −729​

 

Page 5 Exercise 17 Answer

We need to simplify the given expression (4⋅10)+(5⋅100)

Multiplication is one of the basic arithmetic operations. The result of which is termed to be the product.

Adding a number to a certain time is simplified as the form of multiplication.

In multiplication, the product of two positive numbers or two negative numbers will result in a positive number.

The product of a negative and a positive number will result in a negative number.

Performing multiplication on the given numbers and adding the result, we get,

Real Numbers Page 5 Exercise 17 Answer
The simplification of the given number results in (4.10) + (5.100) = 540

 

Page 5 Exercise 19 Answer

We need to simplify the given expression (2.100)+(7.10)

Multiplication is one of the basic arithmetic operations. The result of which is termed to be the product.

Adding a number to a certain time is simplified as the form of multiplication.

In multiplication, the product of two positive numbers or two negative numbers will result in a positive number.

The product of a negative and a positive number will result in a negative number.

Performing multiplication on the given numbers and adding the result, we get,

Real Numbers Page 5 Exercise 19 Answer
The simplification of the given number results in (2.100)+(7.10) = 270

 

Page 5 Exercise 20 Answer

We need to simplify the given expression (9⋅1000)+(4⋅10)

Multiplication is one of the basic arithmetic operations. The result of which is termed to be the product.

Adding a number to a certain time is simplified as the form of multiplication.

In multiplication, the product of two positive numbers or two negative numbers will result in a positive number.

The product of a negative and a positive number will result in a negative number.

Performing multiplication on the given numbers and adding the result, we get,
Real Numbers Page 5 Exercise 20 Answer

The simplification of the given number results in (9⋅1000)+(4⋅10)=9040

 

Envision Math Grade 8 Volume 1 Student Edition Solutions Chapter 1 Real Number Exercise 1.1 Page 5 Exercise 21 Answer

We need to simplify the given expression (3⋅1000)−(2⋅100)

Multiplication is one of the basic arithmetic operations. The result of which is termed to be the product.

Adding a number to a certain time is being simplified as the form of multiplication.

In multiplication, the product of two positive numbers or two negative numbers will result in a positive number.

The product of a negative and a positive number will result in a negative number.

Performing multiplication on the given numbers and subtracting the result, we get,

Real Numbers Page 5 Exercise 21 Answer

The simplification of the given number results (3.1000) – (2.100) = 2800

 

Page 5 Exercise 22 Answer

We need to simplify the given expression (2⋅10)+(7⋅100)

Multiplication is one of the basic arithmetic operations. The result of which is termed to be the product.

Adding a number to a certain time is being simplified as the form of multiplication.

In multiplication, the product of two positive numbers or two negative numbers will result in a positive number.

The product of a negative and a positive number will result in a negative number.

Performing multiplication on the given numbers and adding the result, we get,

Real Numbers Page 5 Exercise 22 Answer
The simplification of the given number results in (2.10) + (7.100) = 720

 

Page 6 Exercise 1 Answer

We need to use the Graphic organizer to help you understand new vocabulary terms such as cube root, irrational number, a perfect cube, perfect square, scientific notation, and square root.

Cube root can be found by finding a number that when multiplied three times by itself gives the original number.

A square root can be found by finding a number that when multiplied two times by itself gives the original number.

If we multiply an integer three times by itself, it will result in a perfect cube.

If we multiply an integer two times by itself, it will result in a perfect square.

Expressing the biggest or the smallest number in decimal form is referred to the scientific notation.

A number that cannot be expressed as a fraction is said to be an irrational number.

 

Cube Root:

Definition – A number which when multiplied 3 times by itself gives the original number.

Example – \(\sqrt[3]{64}=4\)

Irrational number:

Definition – A number that cannot be expressed as a fraction but in decimal form.

Example – 0.24556766666…

Perfect cube:

Definition – The number obtained If we multiply an integer 3 times by itself.

Example – 3×3×3=27

Perfect square:

Definition – The number obtained If we multiply an integer 2 times by itself.

Example – 3×3=9

Scientific notation:

Definition – Expressing the biggest or the smallest number in decimal form.

Example – 1.543543543… = \(1.5 \overline{4} 3\)

Square Root:

Definition – A number which when multiplied 2 times by itself gives the original number.

Example – \(\sqrt[2]{16}=4\)

 

Page 7 Exercise 1 Answer

Given that, Jaylon has a wrench labeled 0.1875 inch and bolts labeled in fractions of an inch. We need to find which size bolt will fit best with the wrench.

The given bolt sizes are \(\frac{3}{8}, \frac{1}{8}, \frac{3}{16}, \frac{1}{4}\)inches.

Solving each fraction to find the equivalent size as that of the wrench given,

\(\frac{3}{8}=0.375\)

\(\frac{1}{8}=0.125\) \(\frac{3}{16}=0.1875\) \(\frac{1}{4}=0.25\)

The bolt size which best fit the wrench is \(\frac{3}{16}\) inch bolt.

\(\frac{3}{16}\) inch size bolt will fit best with the wrench.

 

Envision Math Grade 8 Volume 1 Student Edition Solutions Chapter 1 Real Number Exercise 1.1 Page 7 Exercise 1 Answer

We need to explain how we can write these numbers in the same form.

The given wrench size is 0.1875 inch

This is of in decimal form.

Meanwhile, the given bolt \(\frac{3}{8}, \frac{1}{8}, \frac{3}{16}, \frac{1}{4}\)inches.

This is of fractional form.

We can easily convert the given fractions to decimals by dividing the fractions given.

It can be done as follows,

\(\frac{3}{8}=0.375\) \(\frac{1}{8}=0.125\) \(\frac{3}{16}=0.1875\) \(\frac{1}{4}=0.25\)

We can write the given numbers in the same form by converting the fractions into decimals.

 

Page 7 Exercise 1 Answer

We need to explain why is it useful to write a rational number as a fraction or as a decimal.

A unique feature of a rational number is that it can be written in the form of a fraction.

Not every decimal is denoted to be the rational number.

Only repeating and the terminating decimal can come under the category of rational number.

It is useful to write it as a fraction or a decimal to make the computations easier.

It is useful to write a rational number as a fraction or as a decimal to help make the calculations easier.

 

Page 8 Exercise 1 Answer

Given that, in another baseball division, one team had a winning percentage of 0.444…..We need to determine the fraction of their games the team won.

A repeating decimal can be written as a fraction by assuming the decimal as a variable.

After that, multiply each sides of it by the multiples of 10.

Subtract both expressions to write the repeating decimals as fractions.

The winning percentage is converted to fractions as,

Real Numbers Page 8 Exercise 1 Answer

 

Page 9 Exercise 2 Answer

We need to write the repeating decimal 0.63333… as a fraction.

A repeating decimal can be written as a fraction by assuming the decimal as a variable..

After that, multiply each sides of it by the multiples of 10

Subtract both expressions to write the repeating decimals as fractions.

The decimal is converted to fractions as,

Real Numbers Page 9 Exercise 2 Answer

The repeating decimal 0.6333… is converted to fraction as \(\frac{19}{30}\)

 

Envision Math Grade 8 Volume 1 Student Edition Solutions Chapter 1 Real Number Exercise 1.1 Page 9 Exercise 3 Answer

We need to write the repeating decimal 4.1363636… as a fraction.

A repeating decimal can be written as a fraction by assuming the decimal as a variable..

After that, multiply each sides of it by the multiples of 10.

Subtract both expressions to write the repeating decimals as fractions.

The decimal is converted to fractions as,

Real Numbers Page 9 Exercise 3 Answer

The repeating decimal 4.1363636… is converted to fraction as \(\frac{455}{110}\)

 

Page 10 Exercise 2 Answer

We need to explain why we multiply by a power of 10 when writing a repeating decimal as a rational number.

A repeating decimal can be written as a fraction by assuming the decimal as a variable..

After that, multiply each sides of it by the multiples of 10.

Subtract both expressions to write the repeating decimals as fractions.

The decimal is converted to fractions as,

Real Numbers Page 10 Exercise 2 Answer

We can determine the power of ten to multiply by in the second step at the right is by calculating how many places after the decimal does the given numbers gets repeated.

Here, the given number gets repeated after one decimal place. Thus, the power of ten is one.

This step is done to convert the given repeating number to a fraction.

We can multiply a repeating decimal by a power of 10 when writing a repeating decimal as a rational number to convert it to a fractional number.

 

Page 10 Exercise 3 Answer

We need to explain how we could decide which power of 10 to multiply an equation when writing a decimal with repeating digits as a fraction.

A repeating decimal can be written as a fraction by assuming the decimal as a variable..

After that, multiply each sides of it by the multiples of 10.

Subtract both the expressions to write the repeating decimals as fractions.

The decimal is converted to fractions as,

Real Numbers Page 10 Exercise 3 Answer

We can determine the power of ten to multiply by in the second step at the right is by calculating how many places after the decimal does the given numbers gets repeated.

Here, the given number gets repeated after one decimal place. Thus, the power of ten is one.

We can determine the power of ten to multiply an equation when writing a decimal with repeating digits as a fraction by determining the number of places after the decimal does the given number gets repeated.

 

Envision Math Grade 8 Volume 1 Student Edition Solutions Chapter 1 Real Number Exercise 1.1 Page 10 Exercise 4 Answer

Given that, a survey reported that \(63 . \overline{63}\)% of moviegoers prefer action films. This percent represents a repeating decimal. We need to write it as a fraction.

A repeating decimal can be written as a fraction by assuming the decimal as a variable.

After that, multiply each sides of it by the multiples of 10.

Subtract both expressions to write the repeating decimals as fractions.

The decimal is converted to fractions as,

Real Numbers Page 10 Exercise 4 Answer

The given percent is written as a fraction as \(\frac{700}{11}\)

 

Page 10 Exercise  5 Answer

We need to write the given decimal 2.3181818… as a mixed number.

A repeating decimal can be written as a fraction by assuming the decimal as a variable.

After that, multiply each side of it by the multiples of 10.

Subtract both expressions to write the repeating decimals as fractions.

The decimal is converted to fractions as,
Real Numbers Page 10 Exercise 5 Answer

The mixed fraction of the given repeating decimal is \(x=2 \frac{3.5}{11}\)

 

Page 11 Exercise 10 Answer

Given that, Tomas asked 15 students whether summer break should be longer. He used his calculator to divide the number of students who said yes by the total number of students. His calculator showed the result as 0.9333….. . We need to write this number as a fraction.

A repeating decimal can be written as a fraction by assuming the decimal as a variable.

After that, multiply each side of it by the multiples of 10.

Subtract both expressions to write the repeating decimals as fractions.

The decimal is converted to fractions as,
Real Numbers Page 11 Exercise 10 Answer

The given decimal 0.9333… is equal to \(x=\frac{8.4}{9}\)

 

Page 11 Exercise 12 Answer

We need to write the given decimal \(0 . \overline{8}\) as a fraction.

A repeating decimal can be written as a fraction by assuming the decimal as a variable.

After that, multiply each side of it by the multiples of 10.

Subtract both expressions to write the repeating decimals as fractions.

The decimal is converted to fractions as,

Real Numbers Page 11 Exercise 12 Answer

The given decimal is converted into a fraction as \(x=\frac{8}{9}\)

 

 

Envision Math Grade 8 Volume 1 Student Edition Solutions Chapter 1 Real Number Exercise 1.1 Page 12 Exercise 13 Answer

We need to write the given decimal \(1 . \overline{48}\) as a mixed number.

A repeating decimal can be written as a fraction by assuming the decimal as a variable.

After that, multiply each side of it by the multiples of 10.

Subtract both expressions to write the repeating decimals as fractions.

The decimal is converted to fractions as,
Real Numbers Page 12 Exercise 13 Answer

The given decimal is converted into a mixed number as \(x=1 \frac{48}{99}\)

 

Page 12 Exercise 14 Answer

We need to write the given decimal \(0 . \overline{6}\)

A repeating decimal can be written as a fraction by assuming the decimal as a variable.

After that, multiply each side of it by the multiples of 10.

Subtract both expressions to write the repeating decimals as fractions.

The decimal is converted to fractions as,

Real Numbers Page 12 Exercise 14 Answer

The given decimal is converted into a fraction as \(\frac{6}{9}\)

 

Page 12 Exercise 15 Answer

Given that a manufacturer determines that the cost of making a computer component is $2.161616. We need to write the cost as a fraction and as a mixed number.

A repeating decimal can be written as a fraction by assuming the decimal as a variable.

After that, multiply each side of it by the multiples of 10.

Subtract both expressions to write the repeating decimals as fractions.

The decimal is converted to fractions as,
Real Numbers Page 12 Exercise 15 Answer

The given decimal is converted into a fraction as \(\frac{214}{99}\) and as a mixed number as \(2 \frac{16}{99}\)

 

Envision Math Grade 8 Volume 1 Student Edition Solutions Chapter 1 Real Number Exercise 1.1 Page 12 Exercise 16 Answer

We need to explain the need for the number of repeating digits we use while writing a repeating decimal as a fraction.

A repeating decimal can be written as a fraction by assuming the decimal as a variable.

After that, multiply each side of it by the multiples of 10.

The power of the number ten which we can use to convert the decimal to fraction can be obtained by looking into the number of repeating digits in a decimal.

If the number of repeating digits is two, then the power of ten multiplied with the decimal will also be two.

When writing a repeating decimal as a fraction, the number of repeating digits we use matters the most since it determines the power of ten which we multiply it with the decimal to make it as a fraction.

 

Page 12 Exercise 17 Answer

When writing a repeating decimal as a fraction, we need to explain why does the fraction always have only 9s or 9s and Os as digits in the denominator.

A repeating decimal can be written as a fraction by assuming the decimal as a variable.

After that, multiply each side of it by the multiples of 10.

The power of the number ten which we can use to convert the decimal to fraction can be obtained by looking into the number of repeating digits in a decimal.

If the number of repeating digits is two, then the power of ten multiplied with the decimal will also be two.

The subtraction of any number of the power of ten by one will result in a number 9 or the multiples of it.

This is why the denominator is always 9 or 9 and 0.

The number divided by 9s or 9s and 0s will result in repeating decimals. That is why when we convert that to a fraction, the denominator is always 9s or 9s and 0s.

 

Page 12 Exercise 18 Answer

We need to find the decimal which is equivalent to \(\frac{188}{11}\)

The given fraction is \(\frac{188}{11}\)

Converting the given fraction to a decimal by dividing the fraction, thus we get,

\(\frac{188}{11}=17.090909 \ldots\)

= \(17 . \overline{09}\)

The decimal which is equivalent to \(\frac{188}{11} \text { is (A) } 17 . \overline{09}\)

 

Page 12 Exercise 19 Answer

We need to draw lines to connect each repeating decimal on the left with an equivalent fraction on the right.

Real Numbers Page 12 Exercise 19 Answer Image 1

Solving each fraction one by one, we get,

\(\frac{58}{165}=0.351515 \ldots=0.35 \overline{1}\) \(\frac{79}{225}=0.351111 \ldots=0.35 \overline{1}\)

\(\frac{13}{37}=0.351351 \ldots=0.3 \overline{5}\) 1

\(\frac{8}{45}=0.1777 \ldots=0.1 \overline{7}\) \(\frac{17}{99}=0.171717 \ldots=0 . \overline{17}\)

Real Numbers Page 12 Exercise 19 Answer Image 2

 

Envision Math Grade 8 Volume 1 Student Edition Solutions chapter Standards for Mathematical Practice Exercise 1

Envision Math Grade 8 Volume 1 Student Edition Solutions chapter Standards for Mathematical Practice Exercise 1

Page 16 Exercise 1 Answer

Given Nori, her friend, and her mother bought a baseball game ticket package. The package includes good seats, lunch, and a chance to get autographs from players. The total cost for the three of them is $375.

The objective is to find an equation of that shows how much each of them still owes and the other question to consider is have the problem been solved before.

The amount that each still owes can be found by defining a variable to unknown and use the known quantities.

Find the equation of that each owes.

Nori, her friend, and her mother bought a baseball game ticket package.

The package includes good seats, lunch, and a chance to get autographs from players.

The total cost for the three of them is $375.

They each paid a $50 deposit.

Total cost is$375

Each paid $50 deposit.

Define a variable.
​x  =  $50
y  =  $50
z  =  $50

Total amount paid as deposit is,

x + y + z = $50 + $50 + $50

= $150

Find the total amount that has to be pay.

Total cost of the ticket is$375

= $375 − $150

=$225

Find the amount that each still owes.

Total amount they owe divided by 3.

= $225 ÷ 3

Page 16 Exercise 1 Answer
= $75

The amount that each still owes is $75.

I have solved similar problems before.

The final answer is that each still owes $75 and the similar problem has been solved before.

Envision Math Grade 8 Volume 1 Student Edition Solutions chapter Standards for Mathematical Practice Exercise 1

Envision Math Grade 8 Standards For Mathematical Practice Exercise 1 Solutions

Page 16 Exercise 2 Answer

Given Nori, her friend, and her mother bought a baseball game ticket package. The package includes good seats, lunch, and a chance to get autographs from players. The total cost for the three of them is $375.

The objective is to find that what information are necessary and what are not necessary.

The necessary and unnecessary information can be found by observing the problem.

Find what information are necessary and what are not necessary.

Nori, her friend, and her mother bought a baseball game ticket package.

The package includes good seats, lunch, and a chance to get autographs from players.

The total cost for the three of them is $375.

They each paid a $50 deposit.

Necessary information:

The total cost for the three of them is $375.

They each paid a $50 deposit.

Unnecessary information:

The package includes good seats, lunch, and a chance to get autographs from players

The necessary information is that the total cost for the three of them is$375 and they each paid a $50 deposit.

The unnecessary information is the package includes good seats, lunch, and a chance to get autographs from players.

 

Envision Math Grade 8 Volume 1 Student Edition Solutions chapter Standards for Mathematical Practice Exercise 1 Page 16 Exercise 3 Answer

Given Nori, her friend, and her mother bought a baseball game ticket package. The package includes good seats, lunch, and a chance to get autographs from players. The total cost for the three of them is $375.

The objective is to check whether the answer make sense.

The answer whether it makes sense or not can be found using the results we obtained.

Check whether the answer make sense.

Nori, her friend, and her mother bought a baseball game ticket package. The package includes good seats, lunch, and a chance to get autographs from players. The total cost for the three of them is $375.

The answer found is that the amount that each still owes is $75.

Yes, it makes send because total amount paid is $375.

For each of them the price of the ticket will be $150

Subtract total amount paid minus total deposit amount.

= $375 − $150

= $225

Divide the amount into three,

= $ 225÷3
Page 16 Exercise 3 Answer
= $ 75

Yes, the answer makes sense.

Envision Math Grade 8 Volume 1 Standards For Mathematical Practice Answers

Page 16 Exercise 4 Answer

Given Nori, her friend, and her mother bought a baseball game ticket package. The package includes good seats, lunch, and a chance to get autographs from players. The total cost for the three of them is $375.

The objective is to find whether the solution pathway is same as the classmate.

The amount that each still owes can be found by defining a variable to unknown and use the known quantities.

Find whether the solution pathway is same as the classmate.
Nori, her friend, and her mother bought a baseball game ticket package. The package includes good seats, lunch, and a chance to get autographs from players. The total cost for the three of them is $375.

The solution pathway is,

Total cost is $375

Each paid $50 deposit.

Define a variable.
​x = $50
y = $50
z = $50

Total amount paid as deposit is,
x + y + z = $50 + $50 + $50

= $150

Find the total amount that has to be pay.

Total cost of the ticket is $375

= $375 − $150

= $225

Find the amount that each still owes.

Total amount they owe divided by3.

​= $225 ÷ 3
Page 16 Exercise 4 Answer

= $75

The amount that each still owes is $75.

The solution pathway is same for me as well as for my classmate.

Envision Math Grade 8 Student Edition Solutions For Standards For Mathematical Practice Exercise 1

Page 18 Exercise 2 Answer

Given Michael’s class is conducting an experiment by tossing a coin. Tails has come up 5 times in a row. That means the next toss will land heads up.

The objective is to find what arguments can be present to defend the conjecture.

The conjecture can be found using the information provided.

Find what arguments can be present to defend the conjecture.

Michael’s class is conducting an experiment by tossing a coin.

The table below shows the results of the last tosses.

Page 18 Exercise 2 Answer

The two outcomes of the toss of a coin are heads or tails. For any individual toss of the coin, the outcome will be either heads o. tails. The two outcomes (heads or tails) are therefore mutually exclusive; if the coin comes up heads on a single toss, it cannot come up tails on the same toss.

The arguments that can be present to defend the conjecture is,

A coin can land on heads or tails, so there are two equally likely outcomes.

Because there may be either head or tail.

The arguments that can be present to defend the conjecture is,

A coin can land on heads or tails, so there are two equally likely outcomes.

Solutions For Envision Math Grade 8 Exercise 1 Standards For Mathematical Practice

Envision Math Grade 8 Volume 1 Student Edition Solutions chapter Standards for Mathematical Practice Exercise 1 Page 18 Exercise 3 Answer

Given Michael’s class is conducting an experiment by tossing a coin. The table below shows the results of the last 9 tosses.

The objective is to find what conjecture can be made about the solution to the problem.

The conjecture can be found using the information provided.

Find what conjecture can be made about the solution to the problem.

Michael’s class is conducting an experiment by tossing a coin.

The table below shows the results of the last 9 tosses.

Page 18 Exercise 3 Answer

 

The conjecture that can be made about the solution to the problem is,

Total observations=25

Required outcome Tails {T,T,T,T,T}

This can occur only ONCE!

The conjecture made is as there are continuous five tails, this may end up with head at next toss.

Envision Math Exercise 1 Solutions For Grade 8 Standards Practice

Page 19 Exercise 1 Answer

Given the class decided to toss two coins at the same time. They wanted to decide whether it is more likely that both coins will show the same side, heads-heads or tails-tails, or more likely that the coins will show one heads and one tails.

The objective is to find the representation that is used to show the relationship among quantities or variables.

The representation can be found using the modelling capability.

Find the representation that is used to show the relationship among quantities or variables.

The class decided to toss two coins at the same time.

They wanted to decide whether it is more likely that both coins will show the same side, heads-heads or tails-tails, or more likely that the coins will show one heads and one tails.

The possible outcomes are, HH, TT, TH, & HT

Page 19 Exercise 1 Answer Image 1

Representation of the outcomes is,

The representation of the relationship among the quantities is,

Page 19 Exercise 1 Answer Image 2

Page 19 Exercise 2 Answer

Given the class decided to toss two coins at the same time. They wanted to decide whether it is more likely that both coins will show the same side, heads-heads or tails-tails, or more likely that the coins will show one heads and one tails.

The objective is to find the way to make our model to work better.

The representation can be found using the modelling capability.

Find the way to make our model to work better.

The class decided to toss two coins at the same time.

They wanted to decide whether it is more likely that both coins will show the same side, heads-heads or tails-tails, or more

likely that the coins will show one heads and one tails.

To make the model better if it doesn’t work, use table representation.

Page 19 Exercise 2 Answer

If the model doesn’t work, the choose better model like table representation

Page 19 Exercise 2 Answer

Page 19 Exercise 3 Answer

Given the class decided to toss two coins at the same time. They wanted to decide whether it is more likely that both coins will show the same side, heads-heads or tails-tails, or more likely that the coins will show one heads and one tails.

The objective is to find the assumption that can be made to simplify the problem.

The simplified problem can be found using the better assumption.

Determine the assumption that can be made to simplify the problem.

The class decided to toss two coins at the same time.

They wanted to decide whether it is more likely that both coins will show the same side, heads-heads or tails-tails, or more likely that the coins will show one heads and one tails.

When we toss two coins simultaneously then the possible of outcomes are:

(Two heads) or (one head and one tail) or (two tails) i.e., in short (H,H)(H,T)(T,T) respectively;

Where H is denoted for head and T is denoted for tail.

The assumption made to simplify the problem is when two coins is tossed simultaneously the possible of outcomes are: (Two heads) or (one head and one tail) or (two tails)

Standards For Mathematical Practice Envision Math Grade 8 Solutions Exercise 1

Envision Math Grade 8 Volume 1 Student Edition Solutions chapter Standards for Mathematical Practice Exercise 1 Page 19 Exercise 4 Answer

 

Given the class decided to toss two coins at the same time. They wanted to decide whether it is more likely that both coins will show the same side, heads-heads or tails-tails, or more likely that the coins will show one heads and one tails.

The objective is to check whether the solution make sense.

The simplified problem can be found using the better assumption.

Check whether the solution make sense.

The class decided to toss two coins at the same time. They wanted to decide whether it is more likely that both coins will show the same side, heads-heads or tails-tails, or more likely that the coins will show one heads and one tails.

The solution obtained is,

The possible outcomes are,

HH, TT, TH, & HT

Page 19 Exercise 4 Answer

 

The solution makes sense.

Yes. The solution or prediction we had makes sense. Because on flipping two coins the outcomes should be both heads or both tails or one head and one tail.

Practice Problems For Envision Math Grade 8 Standards Exercise 1

Page 19 Exercise 5 Answer

Given the class decided to toss two coins at the same time. They wanted to decide whether it is more likely that both coins will show the same side, heads-heads or tails-tails, or more likely that the coins will show one heads and one tails.

The objective is to find is there something that is forgotten or not considered.

The representation can be found using the modelling capability.

Find is there something that is forgotten or not considered.

The class decided to toss two coins at the same time. They wanted to decide whether it is more likely that both coins will show the same side, heads-heads or tails-tails, or more likely that the coins will show one heads and one tails.

There is nothing that is forgotten or not considered while predicting the solution.

Nothing is forgotten or not considered while predicting the solution.

Envision Math Grade 8 Chapter Standards Practice Exercise 1 Worksheet Answers

Page 20 Exercise 1 Answer

Given The Golden Company uses signs in the shape of golden rectangles to advertise its products. In a golden rectangle the length of the longer side is about 1.618 times longer than the shorter side. Draw rectangles to scale to create templates of possible small, medium, and large advertising signs.

The objective is to find whether different tools can be used.

The tools that are to be used can be found by strategical thinking.

Find whether different tools can be used.
The Golden Company uses signs in the shape of golden rectangles to advertise its products. In a golden rectangle the length of the longer side is about times longer than the shorter side.

Draw rectangles to scale to create templates of possible small, medium, and large advertising signs.
Large advertising signs.
Page 20 Exercise 1 Answer Image 1
Medium advertising signs.
Page 20 Exercise 1 Answer Image 2

Small advertising signs.
Page 20 Exercise 1 Answer Image 3

Different tools can be used to make design and technology software’s for drawing.

 

Envision Math Grade 8 Volume 1 Student Edition Solutions chapter Standards for Mathematical Practice Exercise 1 Page 20 Exercise 2 Answer

Given The Golden Company uses signs in the shape of golden rectangles to advertise its products. In a golden rectangle the length of the longer side is about times longer than the shorter side. Draw rectangles to scale to create templates of possible small, medium, and large advertising signs.

The objective is to find what other resources can uses to reach the solution

The tools that are to be used can be found by strategical thinking.

Find what other resources can uses to reach the solution.
The Golden Company uses signs in the shape of golden rectangles to advertise its products. In a golden rectangle the length of the longer side is about times longer than the shorter side.

The other resources that can be used to help reach the solution is technical drawing software where the measurements will be given and content to be advertise will also be given.

The technical drawing software is the resource that is used to reach the solution.

 

Page 21 Exercise 1 Answer

Given the explanation about golden rectangle advertisement and their dimensions.

The objective is to state the meaning of variables and symbols used.

The variables and symbols used can be found using the information provided

State the meaning of variables and symbols used.

The work is precise enough and appropriate.

Draw the shorter side and then multiply that dimension by 1.618 to determine the length of the longer side.

Length L = Shorter side x1.618
Width W =1.618 cm

The variables used are,

L for length of the rectangle.

W for width of the rectangle.

Symbols that are used is,

Equal to =

Multiplication x

The symbols used are equal to and multiplication.

The variables used are L and W.

 

Page 21 Exercise 2 Answer

Given the explanation about golden rectangle advertisement and their dimensions.

The objective is to specify the units of measure using.

The variables and symbols used can be found using the information provided.

State the meaning of variables and symbols used.

The work is precise enough and appropriate.

Draw the shorter side and then multiply that dimension by 1.618 to determine the length of the longer side.

Length L = Shorter side x1.618

Width W =1.618cm

The variables used are,
L for length of the rectangle.
W for width of the rectangle.
Symbols that are used is,
Equal to =

Multiplication x

The units of measure that is specified is centimetre or cm.

The units of measure that is specified is centimetre or cm.

 

Envision Math Grade 8 Volume 1 Student Edition Solutions chapter Standards for Mathematical Practice Exercise 1 Page 21 Exercise 3 Answer

Given the explanation about golden rectangle advertisement and their dimensions.

The objective is to find whether the work is precise or exact enough.

The precision used can be found using the result got.

Find whether the work is precise or exact enough.
Page 21 Exercise 3 Answer

I am using the appropriate tools to make sure that the dimensions of the templates are precise.

The work is precise and exact because the appropriate tools are used.

 

Page 21 Exercise 4 Answer

Given the explanation about golden rectangle advertisement and their dimensions.

The objective is to find whether the explanation carefully formulated.

The variables and symbols used can be found using the information provided.

Find whether the explanation carefully formulated.

Length L = Shorter side x1.618
Width W = 1.618cm

The variables used are,

L for length of the rectangle.

W for width of the rectangle.

Symbols that are used is,

Equal to =

Multiplication x1

The units of measure that is specified are centimetre or cm.

Yes, the information provided are carefully formulated.

Yes, the explanations provided are carefully formulated.

 

Envision Math Grade 8 Volume 1 Student Edition Solutions chapter Standards for Mathematical Practice Exercise 1 Page 22 Exercise 1 Answer

Given that Stuart is studying cell division. The table below shows the number of cells after a certain number of divisions.

The objective is to make a chart that shows drawings of the cell divisions through 10 divisions.

The chart can be found using the table and the explanation provided.

Make a chart that shows drawings of the cell divisions through 10 divisions.

The table below shows the number of cells after a certain number of divisions.
Page 22 Exercise 1 Answer Image 1
The structure for the problem is,
1 cell becomes 2 cells and 2 cells become 4 cells, and so on.
Page 22 Exercise 1 Answer Image 2

The attributes that are used in the drawing is a tree chart to describe the cells and their division.

 

Page 22 Exercise 2 Answer

Given that Stuart is studying cell division. The table below shows the number of cells after a certain number of divisions.

The objective is to find the patterns in numbers that are described.

The patterns in number can be found using observation.

Find the patterns in numbers that are described.

Stuart is studying cell division. The table shows the number of cells after a certain number of divisions.

Initial cell is one and on further cell division, it becomes 2.

2 cells become 4

4 cells become 8 and so on….

1, 2, 4, 8, 16, 32, 64, 128, 256,….

This sequence has a factor of 2 between each number.

Each term (except this first term) is found by multiplying the previous term by 2.

The pattern obtained in a geometric sequence.

The pattern in numbers can be described as GEOMETRIC SEQUENCE.

 

Envision Math Grade 8 Volume 1 Student Edition Solutions chapter Standards for Mathematical Practice Exercise 1 Page 22 Exercise 3 Answer

Given that Stuart is studying cell division. The table below shows the number of cells after a certain number of divisions.

The objective is to find th expressions or equations in different ways.

The patterns in number can be found using observation.

Find the expressions or equations in different ways.

Stuart is studying cell division. The table below shows the number of cells after a certain number of divisions.

1, 2, 4, 8, 16, 32, 64, 128, 256,…..

This sequence has a factor of 2 between each number.

Each term (except the first term) is found by multiplying the previous term by 2.

The pattern obtained in geometric sequence.

The equation of expression that can is noticed is 2n.

Example:

Initial cell is one and on further cell division, it becomes 2.

On second division is should become 4.

For that multiply the cells obtained in initial division by 2.

The expression or equation can be viewed in different ways. The expression we obtained is 2n.

How To Solve Envision Math Grade 8 Standards For Mathematical Practice Exercise 1

Page 23 Exercise 1 Answer

Given the explanation about cell division.

Page 23 Exercise 1 Answer Image 1

The objective is to find the general method or shortcut to solve the problem.

The general methods can be found using simple formulas and observing.

Find the general method or shortcut to solve the problem.

From the figure, it is observed that the cells are divided from one cell.

The general method that can be used to solve the problem is,

Number of cells multiplied by 2 is the result.

It is noticed that when calculations are repeated.

Then we can find more general methods and shortcuts.
Page 23 Exercise 1 Answer Image 2

The final answer is that it can be generalized and the shortcut used is power tables as the cells divided is multiplied by two will give the result.

Page 23 Exercise 2 Answer

Given the explanation about cell division.

The objective is to find that an expression or equation can be derived.

The general methods can be found using the simple formulas and observation.

Find an expression or equation that can be derived from the examples.

The example obtained is,
Page 23 Exercise 2 Answer

The expression or equation that can be derived is,

N = n x 2

Equation:

4 * 2 = 8

Where N = total number of cells.

n = number of cells divided.

The final answer is that an expression that can be derived is n N = n x 2

Envision Math Grade 8 Standards For Mathematical Practice Exercise 1 Explained

Envision Math Grade 8 Volume 1 Student Edition Solutions chapter Standards for Mathematical Practice Exercise 1 Page 23 Exercise 3 Answer

Given the explanation about cell division.
Page 23 Exercise 3 Answer

The objective is to find that how reasonable are the results.

The general methods can be found using the simple formula and observation.

Find that how reasonable are the results.

The expression or equation that can be derived is,

Where N = total number of cells.
n = number of cells divided.

The result obtained is so reasonable that, using expression we obtained, number of cells that are divided can be found out easily without drawing 1024 cells in a chat that takes time hardly.

The final answer is that, the result we are getting is so reasonable that using the formula we obtained, it can be used to solve the cell divide.

Envision Math Grade 8 Chapter 1 Real Numbers Topic 1 Solutions

Envision Math Grade 8 Volume Student Edition Solutions Chapter 1 Real Numbers Topic 1

Page 37 Exercise 1 Answer

Irrational numbers cannot be represented as a fraction.

Irrational numbers are non-terminating and non-repeating in nature.

Only terminating and repeating decimals can be represented as a fraction.

Rational numbers are terminating and repeating in nature.

Only rational numbers can be represented as a fraction while irrational numbers cannot.

Terminating and repeating decimals are known as rational numbers while non-repeating decimals are known as irrational numbers.

Envision Math Grade 8 Chapter 1 Topic 1 Solution Guide

Envision Math Grade 8 Volume Student Edition Solutions Chapter 1 Real Numbers Topic 1 Page 37 Exercise 3 Answer

We need to find whether the number √8 is greater than, less than or equal to 4.

Finding where the given square root number lie in the number line, thus,

√4 < √8 < √9

2 < √8 < 3

Thus, the value of √8 is less than the number 3.

Therefore, the number √8 is less than the number 4.

The number √8 is less than the number 4.

Envision Math Grade 8 Volume Student Edition Solutions Chapter 1 Real Numbers Topic 1

Page 37 Exercise 4 Answer

We need to solve m2 = 14

Solving the given expression, we get,

m2 = 14

m = √14

m = ±√14

The solutions are m = +√14 and m = −√14

Envision Math Grade 8 Chapter 1 Topic 1 Real Numbers Solutions

Envision Math Grade 8 Volume Student Edition Solutions Chapter 1 Real Numbers Topic 1 Page 37 Exercise 6 Answer

We need to write \(1 . \overline{12}\) as a mixed number.

Writing the given numbers as a mixed fraction, we get,

x = 1.121212…

100x = 112.121212…

100x – x = 112.121212… – 1.121212…

99x = 112 – 1

99x = 111

\(x=\frac{111}{99}\) \(x=1 \frac{12}{99}\)

The number is represented as mixed fraction as \(x=1 \frac{12}{99}\)

Real Numbers Topic Solutions Grade 8 Envision Math

Envision Math Grade 8 Volume Student Edition Solutions Chapter 1 Real Numbers Topic 1 Page 38 Exercise 1 Answer

Given that the table shows the results of the draw. The students who drew rational numbers will form the team called the Tigers. The students who drew irrational numbers will form the team called the Lions. We need to list the members of each team.

 

real numbers

 

The students who drew rational numbers will form the team called the Tigers.

The students who drew irrational numbers will form the team called the Lions.

Lydia drawn √38

The number 38 is not a perfect square. Hence, it is an irrational number.

Marcy drawn \(6.3 \overline{4}\)

The number is repeating in nature. Hence, it is a rational number.

Caleb drawn √36

The number 36 is a perfect square. Hence, it is a rational number.

Ryan drawn 6.343443444…

The number is non terminating and non-repeating. Hence, it is an irrational number.

Anya drawn \(6 . \overline{34}\)

The number is repeating in nature. Hence, it is a rational number.

Chan drawn √34

The number 34 is not a perfect square. Hence, it is an irrational number.

Lydia – Irrational number

Marcy – Rational number

Caleb – Rational number

Ryan – Irrational number

Anya – Rational number

Chan – Irrational number

Team Tigers:

Marcy, Caleb, Anya

Team Lions:

Lydia, Ryan, Chan

Team Tigers:

Marcy, Caleb, Anya

Team Lions:

Lydia, Ryan, Chan

Envision Math Grade 8 Chapter 1 Topic 1 Answers

Envision Math Grade 8 Volume Student Edition Solutions Chapter 1 Real Numbers Topic 1 Page 38 Exercise 2 Answer

Given that the student on each team who drew the greatest number will be the captain of that team. We need to find who will be the captain of the Tigers.

The numbers drawn by the members of the team Tigers will be,

Marcy – \(6.3 \overline{4}\)

Cleb – √36

Anya – \(6 . \overline{34}\)

Thus, the numbers are,

\(6.3 \overline{4}\) = 6.344444…

√36 = 6

\(6 . \overline{34}\) = 6.343434…

The greatest number among them will be \(6.3 \overline{4}\)

Therefore, Marcy will be the captain of the Tigers.

Marcy will be the captain of the Tigers.

 

Multiplying Rational Numbers: Solutions for Envision Math Grade 8 Exercise 1.5

Multiplying Rational Numbers: Solutions For Envision Math Grade 8 Exercise 1.5

Envision Math Grade 8, Volume 1, Chapter 1: Real Number

Page 31 Exercise 1 Answer

Given that, Janine can use up to 150 one-inch blocks to build a solid, cube-shaped model. We need to find the dimensions of the possible models that she can build. Also, find how many blocks would Janine use for each model.

Find the perfect cubes from 0 to 150

​1 × 1 × 1 = 1

2 × 2 × 2 = 8

3 × 3 × 3 = 27

4 × 4 × 4 = 64

5 × 5 × 5 = 125

6 × 6 × 6 = 216

The total number of blocks given is 150. Thus, all possible dimensions less than 150 are our solutions.

The dimensions of the possible models that she can build will be,

2 × 2 × 2

3 × 3 × 3

4 × 4 × 4

5 × 5 × 5

Envision Math Grade 8 Volume 1 Student Edition Solutions Chapter 1 Real Number Exercise 1.5

Multiplying Rational Numbers: Solutions for Envision Math Grade 8 Exercise 1.5 Page 31 Exercise 2 Answer

We need to explain how the dimensions of a solid related to its volume.

The dimensions of the possible models that Janine can build will be,
​2 × 2 × 2

3 × 3 × 3

4 × 4 × 4

5 × 5 × 5

The dimensions of a solid are related to its volume since they are building a solid, cube-shaped model.

The volume of the cube will be V = s3 where s is the length of the edge of the cube.

The dimensions of a solid are related to its volume since the dimensions consist of nothing but the length of the edge of the cube.

 

 

Multiplying Rational Numbers: Solutions For Envision Math Grade 8 Exercise 1.5 Page 31 Exercise 1 Answer

Given that, Janine wants to build a model using \(\frac{1}{2}\)-icnh cubes. We need to find how many \(\frac{1}{2}\)-icnh cubes would she use to build a solid, cube-shaped model with side lengths of 4 inches.

Let x be the number of \(\frac{1}{2}\) inch cube with the side length of 4 inches.

The equation formed from the given information will be,

\(\frac{1}{2} x=4\)

x = 4 x 2

x = 8

Therefore, she needs 8 blocks per side.

Thus, the number of little cubes she needs will be,

V = 8 × 8 × 8 = 512

Therefore, she needs to use 512, \(\frac{1}{2} x=4\) inch cubes to build a cube-shaped model with a side length of 4 inches.

She needs to use 512, \(\frac{1}{2} x=4\) inch cubes to build a cube-shaped model with a side length of 4 inches.

 

Page 32 Question 1 Answer

We need to explain how we can solve equations with squares and cubes.

In order to solve equations with squares, find the number obtained by multiplying the given number two times itself.

For example, if the number is 4

The square of the given number is,

4 × 4 = 16

The square of 4 is 16

In order to solve equations with cubes, find the number obtained by multiplying the given number three times itself.

For example, if the number is 2

The cube of the given number is

2 × 2 × 2 = 8

The cube of 2 is 8

Solve equations with squares by finding the number obtained by multiplying the given number two times itself. Similarly, solve equations with cubes by finding the number obtained by multiplying the given number three times itself.

 

Multiplying Rational Numbers: Solutions For Envision Math Grade 8 Exercise 1.5 Page 32 Exercise 1 Answer

We need to find the side length, s, of the square below.

The area of the square is A=100m2

square
Real Numbers Page 32 Exercise 1 Answer

 

The side of the square will be 10m.

 

Page 32 Exercise 2 Answer

We need to solve x3 = 64

Real Numbers Page 32 Exercise 2 Answer
The value of x = 4

 

Page 33 Exercise 3 Answer

We need to solve a3 = 11
Real Numbers Page 33 Exercise 3 Answer

 

The solutions are c=√27 and c=−√27

 

Multiplying Rational Numbers: Solutions For Envision Math Grade 8 Exercise 1.5 Page 32 Exercise 1 Answer

We need to explain why are there two possible solutions to the equation s2 = 100 And also, we have to explain why only one of the solutions is valid in this situation.

Real Numbers Page 32 Exercise 1 Answer Image

Here, we have taken the value of s as +10 since we know that the value of the length cannot be a negative one.

The value of the length cannot be negative. This is why we have taken only the positive value of s

 

Multiplying Rational Numbers: Solutions For Envision Math Grade 8 Exercise 1.5 Page 34 Exercise 2 Answer

Suri solved the equation x2 = 49 and found that x=7

We need to find the error Suri made.

Real Numbers Page 34 Exercise 4 Answer

The value of x = +7 and x = −7. The values are both positive and negative. This is the error Suri made.

We need to explain why are the solutions to x2 = 17 is irrational.
Real Numbers Page 34 Exercise 4 Answer Image

The solutions are irrational since the square root of 17 is not a perfect square number.

The solutions are irrational since the square root of 17 is not a perfect square.

 

Page 34 Exercise 5 Answer

Given that, If a cube has a volume of 27 cubic centimeters, We need to find the length of each edge by using the volume formula V = s3

Real Numbers Page 34 Exercise 5 Answer
The length of each edge will be 3cm.

 

Multiplying Rational Numbers: Solutions For Envision Math Grade 8 Exercise 1.5 Page 34 Exercise 7 Answer

We need to solve x3 = −215

Real Numbers Page 34 Exercise 7 Answer
The solution is x = \(-\sqrt[3]{215}\)

 

Multiplying Rational Numbers: Solutions for Envision Math Grade 8 Exercise 1.5 Page 35 Exercise 9 Answer

We need to solve a3 = 216
Real Numbers Page 34 Exercise 9 Answer

The solution is a = 6

 

Multiplying Rational Numbers: Solutions For Envision Math Grade 8 Exercise 1.5 Page 35 Exercise 12 Answer

We need to solve y2 = 81
Real Numbers Page 35 Exercise 12 Answer

The solutions are y = +9 and y = −9

 

Page 35 Exercise 13 Answer

We need to solve w3 = 1000

Real Numbers Page 35 Exercise 13 Answer

The solution is w = 10

 

Page 35 Exercise 14 Answer

The area of a square garden is given as A=121ft2. We need to find how long is each side of the garden.
Real Numbers Page 35 Exercise 14 Answer

The length of the side of the garden is 111ft

 

Page 35 Exercise 15 Answer

We need to solve b2 = 77
Real Numbers Page 35 Exercise 15 Answer

The solutions are b = +√77 and b = −√77

 

Page 36 Exercise 19 Answer

Given that, Manolo says that the solution of the equation g2 = 36 is g = 6 because 6 × 6 = 36

Check whether Manolo’s reasoning is complete or not
Real Numbers Page 36 Exercise 19 Answer

Therefore, Manolo’s reasoning is wrong.

 

Page 36 Exercise 20  Answer

We need to solve \(\sqrt[3]{-512}\)
Real Numbers Page 36 Exercise 20 Answer

The solution is \(\sqrt[9]{-512}=-8\)

We need to explain how we can check that our result \(\sqrt[3]{(-8)^3}\).

To verify the result, find the cube of the obtained result,

Thus, we get,

−8 × −8 × −8 = −512

Thus, our obtained result is correct.

The cube of -8 is -512. Hence, it is verified.

 

Multiplying Rational Numbers: Solutions For Envision Math Grade 8 Exercise 1.5 Page 36 Exercise 21 Answer

Given that, Yael has a square-shaped garage with 228 square feet of floor space. She plans to build an addition that will increase the floor space by 50%. We need to find the length, to the nearest tenth, of one side of the new garage.
Real Numbers Page 36 Exercise 21 Answer

The length, to the nearest tenth, of one side of the new garage is 18.5ft

 

Page 36 Exercise 22 Answer

Given that the Traverses are adding a new room to their house. The room will be a cube with a volume of 6,859 cubic feet. They are going to put in hardwood floors, which costs $10 per square foot. We need to find how much will the hardwood floors cost.

The given volume is 6859ft3
Real Numbers Page 36 Exercise 22 Answer

The hardwood floor costs 3610 dollars.

 

 

Multiplying Rational Numbers: Solutions For Envision Math Grade 8 Exercise 1.5 Page 36 Exercise 23 Answer

Given that, while packing for their cross-country move, the Chen family uses a crate that has the shape of a cube.

If the crate has the volume V=64 cubic feet, we need to find the length of one edge.
Real Numbers Page 36 Exercise 23 Answer Image 1

The length of one edge will be 4ft

Given that, While packing for their cross-country move, the Chen family uses a crate that has the shape of a cube.

The Chens want to pack a large, framed painting. If the framed painting has the shape of a square with an area of 12 square feet, we need to find the painting will fit flat againsts a side of the crate.
Real Numbers Page 36 Exercise 23 Answer Image 2

Thus, the area of the cube is more than that of the given square. Thus, it can fit flat on the floor.

Envision Math Grade 8 Volume 1 Chapter 1 Exercise 1.3 Real Number Solutions

Envision Math Grade 8 Volume 1 Chapter 1 Exercise 1.3 Real Number Solutions

Page 19 Exercise 1 Answer

Given that, Courtney and Malik are buying a rug to fit in a 50-square-foot space. We need to determine which rug should they purchase.
Real Numbers Page 19 Exercise 1 Answer

We need to buy a rug to fit in a 50-square-foot space. Therefore, we need to buy a rug which is smaller than this.

The first rug will be,

7ft × 7ft = 49ft2

The second rug is of circle-shaped, thus, its area will be,

A = πr2

A = \(\frac{22}{7} \times 4^2\)

A = 50.2857

The third rug area will be,

⇒ \(6 \mathrm{ft} \times 8 \frac{1}{2} \mathrm{ft}=6 \mathrm{ft} \times \frac{17}{2} \mathrm{ft}\)

=3 × 17ft2

= 51ft2

​Only the first rug is smaller than the 50 square foot space. Therefore, it is

Courtney and Malik should purchase the first rug whose dimensions are 7ft x 7ft

Envision Math Grade 8 Volume 1 Student Edition Solutions Chapter 1 Real Number Exercise 1.3

Envision Math Grade 8 Volume 1 Chapter 1 Exercise 1.3 Real Number Solutions

Envision Math Grade 8 Volume 1 Chapter 1 Exercise 1.3 Real Number Solutions Page 19 Exercise 1 Answer

We need to explain how we have decided which rug Courtney and Malik should purchase.

As we need to find a rug which has to be fit in the space of 50 square foot.

We need to buy a rug which is smaller than the space.

Thus, we need to find the areas of all three rugs and then decide which one’s area is less than 50 square foot.

The area of the first rug is, A=49ft2

The area of the second rug is, A=50.2857ft2

The area of the third rug is, A = 51ft2

We have decided which rug to buy by finding the areas of all three rugs and determining which one’s area is smaller than 50 square foot.

 

Page 20 Question 1 Answer

We need to explain how we can compare and order rational and irrational numbers.

We can compare and order rational and irrational numbers by the following ways:

Irrational numbers cannot be represented as a fraction.

Irrational numbers are non-terminating and non-repeating in nature.

Only terminating and repeating decimals can be represented as a fraction.

Rational numbers are terminating and repeating in nature.

Only rational numbers can be represented as a fraction while irrational numbers cannot.

Rational numbers are terminating and repeating while irrational numbers are non-terminating and non-repeating in nature.

Envision Math Grade 8 Exercise 1.3 Real Numbers Answers

Envision Math Grade 8 Volume 1 Chapter 1 Exercise 1.3 Real Number Solutions Page 20 Exercise 1 Answer

We need to determine which decimals we can use to find a better approximation.

Find the two closest consecutive perfect squares of the given number √74

The perfect squares which is closest to them is √64 and √81

Thus, the given number √74 is between the numbers 8 and 9

As we can see that the number √74 is closest to 9 more than the number 8.

Thus, ​8 < √74 < 9

8.5 < √74

Thus, squaring the decimals above 8.5 and below 9 we get,

8.6 × 8.6 = 73.96

8.7 × 8.7 = 75.69

8.8 × 8.8 = 77.44

8.9 × 8.9 = 79.21

Therefore, the number √74 is about 8.6ft

For finding the better approximation, square decimals between 8.5 and 8.9 since √74 > 8.5

 

Page 20 Exercise 1 Answer

We need to find between which two whole numbers is √12

The two closest perfect square roots of the given number √12 is,√9 and √16

Thus,

√9 < √12 < √16

3 < √12 < 4

Thus, the given number is between 3 and 4

The number √12 lies between the whole numbers 3 and 4

 

Envision Math Grade 8 Volume 1 Chapter 1 Exercise 1.3 Real Number Solutions Page 21 Exercise 2 Answer

We need to compare and order the following numbers:

√11, \(2 \frac{1}{4}\), −2.5, 3.6, −3.97621…

Finding where the given square roots numbers lie in the number line, thus,

√9 < √11 < √16

3 < √11 < 4

3 < √11 < 3.5

Since it is closer to the number 9 than 16.

\(2 \frac{1}{4}\) = 2.250

Thus, ordering the given numbers, we get,

\(-3.97621 \ldots<-2.5<2 \frac{1}{4}<\sqrt{11}<3 . \overline{6}\)

Comparing and ordering the given numbers, we get,

\(-3.97621 \ldots<-2.5<2 \frac{1}{4}<\sqrt{11}<3 . \overline{6}\)

 

Page 22 Exercise 1 Answer

We need to explain how we can compare and order rational and irrational numbers.

Irrational numbers cannot be represented as a fraction.

Irrational numbers are non-terminating and non-repeating in nature.

Only terminating and repeating decimals can be represented as a fraction.

Rational numbers are terminating and repeating in nature.

Only rational numbers can be represented as a fraction while irrational numbers cannot.

Find some rational number closer to the irrational number. Then compare the other one with the obtained estimate for the irrational number to order them.

Find some rational number closer to the irrational number. Then compare the other one with the obtained estimate for the irrational number to order them.

 

Envision Math Grade 8 Volume 1 Chapter 1 Exercise 1.3 Real Number Solutions Page 22 Exercise 3 Answer

We need to find which one is a better approximation of √20. The given approximated values are 4.5 or 4.47

Finding where the given square root number lie in the number line, thus,

√16 < √20 < √25

4 < √20 < 5

The number 20 is closer to 4 than 5.

Thus, 4 < √20 < 4.5

Thus, squaring the decimal values to find a better estimate, we get,

4.47 × 4.47 = 19.9809

4.5 × 4.5 = 20.25

Thus, 4.47 is a better estimate.

4.47 is a better estimate of √20

Real Number Solutions Grade 8 Exercise 1.3 Envision Math

Envision Math Grade 8 Volume 1 Chapter 1 Exercise 1.3 Real Number Solutions Page 22 Exercise 5 Answer

We need to approximate √18 to the nearest tenth and plot the number on a number line.

Finding where the given square root number lie in the number line, thus,

√16 < √18 < √25

4 < √18 < 5

4 < √18 < 4.5

since √18 is closer to 4 than 5.

Thus, squaring the decimal values to find a better estimate, we get,

4.1 × 4.1 = 16.81

4.2 × 4.2 = 17.64

4.3 × 4.3 = 18.49

4.4 × 4.4 = 19.36

Thus, the number 4.2 is the better estimate.
Real Numbers Page 22 Exercise 5 Answer
The number 4.2 is the better estimate.
Real Numbers Page 22 Exercise 5 Answer

 


Envision Math Grade 8 Volume 1 Chapter 1 Exercise 1.3 Real Number Solutions Page 22 Exercise 6 Answer

We need to compare 5.7145… and √29 and find which one is greater than the other.

Finding where the given square root number lie in the number line, thus,

√25 < √29 < √36

5 < √29 < 6

5 < √29 < 5.5

The number √29 is closer to 5 than 6

Thus, squaring the decimal values to find a better estimate, we get,

5.2 × 5.2 = 27.04

5.3 × 5.3 = 28.09

5.4 × 5.4 = 29.16

Thus, 5.3 is a better estimate of √29

Therefore, √29 < 5.7145…

Comparing the numbers, we get, √29 < 5.7145…

 

Page 23 Exercise 9 Answer

We need to compare -1.9612… and -√5 and find which one is greater than the other.

Finding where the given square root number lie in the number line, thus,

−√4 < −√5 < −√9#

−2 < −√5 < −3

Therefore, ordering the given numbers we get,

−√5 < -1.96312…

Ordering the numbers, we get,

−√5 < -1.96312…

Envision Math Grade 8 Chapter 1 Exercise 1.3 Solutions

Envision Math Grade 8 Volume 1 Chapter 1 Exercise 1.3 Real Number Solutions Page 24 Exercise 13  Answer

Given that, Rosie is comparing √7 and 3.4444….. She says that

√7 > 3.4444… because √7 = 3.5.

We need to check whether the comparison is correct or not.

Finding where the given square root number lie in the number line, thus,

√4 < √7 < √9

2 < √7 < 3

2.5 < √7 < 3

Thus, √7 < 3.4444…

The comparison made by Rosie is incorrect.

Given that, Rosie is comparing √7 and 3.4444….. She says that

√7 > 3.4444… because √7 = 3.5.

We need to find the mistake Rosie likely made.

Finding where the given square root number lie in the number line, thus,

√4 < √7 < √9

2 < √7 < 3

2.5 < √7 < 3

Thus,

√7 < 3.444…

√7 = 2.646

The comparison made by Rosie is incorrect since the value of √7 = 2.646

 

Envision Math Grade 8 Volume 1 Chapter 1 Exercise 1.3 Real Number Solutions Page 24 Exercise 14 Answer

We need to approximate −√23 to the nearest tenth. Also, draw the point on the number line.

Finding where the given square root number lie in the number line, thus,

−√16 > −√23 > −√25

−4 > −√23 > −5

−4.5 > −√23 > −5

Thus, squaring the decimal values to find a better estimate, we get,

4.6 × 4.6 = 21.16

4.7 × 4.7 = 22.09

4.8 × 4.8 = 23.04

4.9 × 4.9 = 24.01

So, a better approximate is -4.7

The better approximate is -4.7
Real Numbers Page 24 Exercise 14 Answer

Envision Math 8th Grade Exercise 1.3 Step-By-Step Real Number Solutions

 

Envision Math Grade 8 Volume 1 Chapter 1 Exercise 1.3 Real Number Solutions Page 24 Exercise 15  Answer

Given that, the length of a rectangle is twice the width. The area of the rectangle is 90 square units. Note that you can divide the rectangle into two squares.

We need to find an irrational number represents the length of each side of the squares.

The given area of the rectangle is 90
square units.
Dividing the given area of the rectangle into two equal squares, we get,

\(\frac{90}{2}=45\)

The area of the square is 45 square units.

The length of each side of the square is,

Area = side2

45 = s2

s = √45

An irrational number represents the length of each side of the squares is √45

Given that the length of a rectangle is twice the width. The area of the rectangle is 90 square units. Note that you can divide the rectangle into two squares.

We need to estimate the length and width of the rectangle.

From part (a), we have divided the rectangle into two equal squares of length of each side is a = √45
Real Numbers Page 24 Exercise 15 Part (b) Answer

The width of the rectangle will be a

Thus,

a = √45

√36 < √45 < √49

6 < √45 < 7

6.5 < √45 < 7

Thus, squaring the decimal values to find a better estimate, we get,

6.6 × 6.6 = 43.56

6.7 × 6.7 = 44.89

6.8 × 6.8 = 46.24

Thus, a = 6.7

The length of the rectangle will be,

l = 2a

l = 2 × 6.7

l = 13.4

The width is l = a = 6.7

The length and width of the rectangle is 6.7,13.4 respectively.

How To Solve Real Numbers Exercise 1.3 In Envision Math Grade 8

Envision Math Grade 8 Volume 1 Chapter 1 Exercise 1.3 Real Number Solutions Page 24 Exercise 17  Answer

The area of a square poster is 31 square inches. We need to find the length of one side of the poster to the nearest whole inch.

The given area of the square poster is 31 square inches.

The length of one side of the poster is,

A = s2

31 = s2

s = √31

Finding where the given square root number lie in the number line, thus,

√25 < √31 < √36

5 < √31 < 6

The number √31 is closer to 6 than 5.

The length of one side of the poster to the nearest whole inch is 6.

The area of a square poster is 31 square inches. We need to find the length of one side of the poster to the nearest tenth of an inch.

The given area of the square poster is 31 square inches.

The length of one side of the poster is s=√31

Finding where the given square root number lie in the number line, thus,

√25 < √31 < √36

5 < √31 < 6

5.5 < √31 < 6

Thus, squaring the decimal values to find a better estimate, we get,

5.5 × 5.5 = 30.25

5.6 × 5.6 = 31.36

5.7 × 5.7 = 32.49

5.8 × 5.8 = 33.64

Therefore, the length of one side of the poster to the nearest tenth of an inch is 5.6

The length of one side of the poster to the nearest tenth of an inch is 5.6

 

David Burton Elementary Number Theory Solutions Chapter 3 Primes And Their Distribution Exercise 3.2

David Burton Elementary Number Theory Solutions Chapter 3 Primes And Their Distribution

Page 49 Problem 1 Answer

Given ; p ≤ √701

To find : Determine whether the integer 701 is prime by testing all primes

here we will factorize the 701 and test the result if it prime or not and do the sam for 1009

we have p ≤ √701

p ≤ √701 ≤ 27,p = 2,3,5,7,11,13,17,19,23

but none of them divides 701 , thus 701 is prime.

p ≤ √1009 ≤ 32,p = 2,3,5,7,11,13,17,19,23,29,31

but none of them divides 1009 , thus 1009 is prime.

Hence we conclude that both the number 701,1009 are prime

David Burton Elementary Number Theory Chapter 3 Exercise 3.2 Solutions

Page 49 Problem 3 Answer

Given ; Given that p/n for all primes p ≤ \(\sqrt[3]{n}\),

To find : show that n > 1 is either a prime or the product of two primes

here we will Assume to the contrary that n contains at least three prime factors

assume n = p1p2⋯pk,k ≥ 3

The first three primes factors are p1,p2,p3 then

p1 ∣ n,p2 ∣ n,p3 ∣ n

⟹ p1p2p3 ∣ n ⟹ p ≥ p1p2p3

Since p ∤ n for all p ≤ \(\sqrt[3]{n}\) then

p1 > \(\sqrt[3]{n}\),p2 > \(\sqrt[3]{n}\),p3 > \(\sqrt[3]{n}\)

Thus p1p2p3 > n contradiction, thus n > 1 is either a prime or the product of two prime

Hence we conclude that if p1p2p3 > n contradiction, thus n > 1 is either a prime or the product of two primes.

David Burton Elementary Number Theory Solutions Chapter 3 Primes And Their Distribution Exercise 3.2

Page 49 Problem 4 Answer

Given ; √p is irrational for any prime p

To find ; Establish the following facts:

here we will asume √p is rational number with p as prime number

Let p is fixed prime number.

Assume that √p is rational,

i.e. √p = \(\frac{k}{l}\) for some positive integers k and l such that gcd(k,l) = 1.

Then must be p = \(\frac{k^2}{l^2}\), also l{2}p = k{2}.

From the last equality, we have that l2 and m2.

Therefore, must be l = 1, because gcd(k,l) = 1.

So that, must be p = m{2}, but this is contradiction, because does not exists prime number which is perfect square!

Hence, the proof!

Hence we have proved that p = m{2},but this is contradiction, because does not exists prime number which is perfect square!

Given ; If a is a positive integer and \(\sqrt[n]{a}\) is rational, then \(\sqrt[n]{a}\) must be an integer

To find; Establish the following facts:

If a is a positive integer and \(\sqrt[n]{a}\) is rational,

we need to show that \(\sqrt[n]{a}\) is an integer.

If \(\sqrt[n]{a}\) is rational, then exist the numbers k and l such that \(\sqrt[n]{a}\) = \(\frac{k}{l}\) and gcd(k,l) = 1.

From \(\sqrt[n]{a}\) = \(\frac{k}{l}\) we have that a = \(\frac{k^n}{l^n}\),

also lna = kn.

Therefore, ln divides kn!

So that, must be l = 1 because gcd(k,l) = 1.

Finally, \(\sqrt[n]{a}\) is an integer!

Hence we conclude that lna = kn. Therefore, ln divides kn! So that, must be l = 1 because gcd(k,l) = 1.

Finally, \(\sqrt[n]{a}\) is an integer!

We have Given ; n ≥ 2,\(\sqrt[n]{n}\) is irrational.

To find : we have to Establish the following facts:

Here we will use the fact 2n > n

If a is a positive integer and \(\sqrt[n]{a}\) is rational,

we need to show that \(\sqrt[n]{a}\) is an integer.

If \(\sqrt[n]{a}\) is rational

Then exist the numbers k and l such that \(\sqrt[n]{a}\) = \(\frac{k}{l}\) and gcd(k,l) = 1.

From \(\sqrt[n]{a}\) = \(\frac{k}{l}\) we have that a = \(\frac{k^n}{l^n}\), also lna = kn.

Therefore, ln divides kn!

So that, must be l = 1 because gcd(k,l) = 1.

Finally, \(\sqrt[n]{a}\) is an integer

If \(\sqrt[n]{n}\) is rational for some integer n ≥ 2,

Then using result from part b it must be integer

From the fact \(\sqrt[n]{n}\) > 1 and preceding fact,

we obtain that \(\sqrt[n]{n}\) ≥ 2.

So that, must be n ≥ 2n.

Further, from the fact n < 2n we have the contradiction!

Finally, \(\sqrt[n]{n}\) is irrational!

Hence we obtain that \(\sqrt[n]{n}\) ≥ 2. It must be n ≥ 2n. from the fact n < 2n we have the contradiction

Finally, \(\sqrt[n]{n}\) is irrational!

 

David Burton Elementary Number Theory Solutions Chapter 3 Primes And Their Distribution Exercise 3.2 Page 49 Problem 6 Answer

Given : Proof of the infinitude of primes.

To find : missing details in given proof.

We will find it.

Here,

Assume only finite numbers p1,…,pn

Let A be the product of any r these primes.

So,

A = pa1⋅…⋅par,ai ∈ {1,2,…,n}

Consider

B = \(\frac{p_1 \cdot \ldots \cdot p_n}{A}\)

= \(\frac{p_1 \cdot \ldots \cdot p_n}{p_{a_1} \cdot \ldots \cdot p_{a_r}}\)

= pb1……..pbs

Where ai ≠ bj

So that,

{ai∣i=1,…,r}∩{bj∣j=1,…,s}=∅

and

{ai∣i=1,…,r}∪{bj∣j=1,…,s}={pi∣i=1,…,n}

Hence, A and B have no common factors.

Then each pk of p1,p2,…,pn divides either A or B, but not both. Since, A > 1,B > 1, then A + B > 1

Therefore, A + B has a prime divisor different from any of the pi, which is a contradiction.

Therefore, We completed the given proof..

Solutions To Chapter 3 Exercise 3.2 Burton Number Theory

Page 49 Problem 7 Answer

Given : Euclid’s proof

To do : Modify the given proof.

Here,

The modify proof is :

Let N > 1 then there exists q (prime number) divide N, since all primes numbers contained in p! = p(p−1)⋯3⋅2⋅1

Now,

q = pi for some i.

Then q∣pi ⟹ q∣1 ⟹ q ≤ 1 which is contradiction.

Hence, there are infinitely many primes.

Therefore,

Modified proof is stated above.

 

David Burton Elementary Number Theory Solutions Chapter 3 Primes And Their Distribution Exercise 3.2 Page 49 Problem 8 Answer

Given : Proof of the infinitude of primes.

To do : Give another proof of the infinitude of primes.

Here,

The another proof of the infinitude of primes:

Let pi ≥ 2 for all i, thus N > 1, then there exists q prime number divides N.

But p1,p2,⋯,pn are all prime numbers, thus q = pi for some i

If q = pi then q ∣ N and q ∣ pi

Then pi = q ∣ p2p3⋯pi-1pi+1⋯pn thus

pi ∣ pk,​2 ≤ k ≤ n is a contradiction.

Hence,

The set of prime numbers is infinite.

Therefore,

Another proof of the infinitude of primes is given above.

Primes And Their Distribution Exercise 3.2 Answers David Burton

David Burton Elementary Number Theory Solutions Chapter 3 Primes And Their Distribution Exercise 3.2 Page 50 Problem 9 Answer

Given : n>2

WE have to prove that there exists a prime p satisfying n < p < n!

We will prove it.

Here,

Let n be an integer such that n > 2, then n!−1 > 1.

Now,

If n!−1 is prime number, we can choose p = n!−1.

From the facts

n!−1 > 2n−1 = n+n−1 > n+1 > n and

n!−1 < n!, we get that n < p < n!−1.

Now,

If n!−1 is not prime, then it has a prime divisor p. Prime divisor p must be bigger than n, because for all positive integer k such that k ≤ n we have k∣n! and they can not be divisors of n!−1.

Hence,

From the facts p∣(n!−1) and n!−1is not prime, we get that p < n!−1.

So , exist prime number p such that n < p < n!−1 < n!

Therefore,

if n > 2, then there exists a prime p satisfying n < p < n!

Given : n > 1,

We have to show that every prime divisor of n!+1 is an odd integer that is greater than n

We will show it.

Here,

Let n be an integer such that n > 1

Then all prime divisors of n!+1 must be bigger than n, because for all positive integer k such that k ≤ n

So, we have k∣n! and they can not be divisors of n! + 1.

Therefore,

For n > 1,every prime divisor of n! + 1 is an odd integer that is greater than n.

 

David Burton Elementary Number Theory Solutions Chapter 3 Primes And Their Distribution Exercise 3.2 Page 50 Problem 10 Answer

Let qn be the smallest prime that is strictly greater than Pn = p1p2⋯pn+1

It has been conjectured that the difference qn−(p1p2⋯pn) always a prime.

We have to confirm this for the first five values of n.

Here,

We have , qn be the smallest prime that is strictly greater than Pn = p1p2⋯pn + 1

It has been conjectured that the difference qn − p1p2⋯pn is always a prime.

Now,

We want to confirm this for the first five values of n: ​

p1 = 2

p2 = 3

p3 = 5

p7,p5 = 11

So,

P1 = 2 + 1 ⇒ 3 ⟹ q1 ⇒ 5,

⇒ q1 − p1 = 5 − 2 ⇒ 3 is prime.

P2 = 2⋅3 + 1 ⇒ 7 ⟹ q2 ⇒ 11,

⇒ q2 − p1p2 = 11 − 6 ⇒ 5 is prime.

P3 = 2⋅3⋅5 + 1 ⇒ 31 ⟹ q3 ⇒ 37,

⇒ q3 − p1p2p3 = 37 − 30 ⇒ 7 is prime.

P4 = 2⋅3⋅5⋅7 + 1 ⇒ 211 ⟹ q4 ⇒ 223,

⇒ q4 − p1p2p3p4 = 223 − 210 ⇒ 13 is prime.

P5 = 2⋅3⋅5⋅7⋅11 + 1 ⇒ 2311 ⟹ q5 ⇒ 2333,

q5 − p1p2p3p4p5 = 2333 − 2310 ⇒ 23 is prime.

Therefore,

The difference qn – (p1p2….pn) always a prime.

Chapter 3 Exercise 3.2 Burton Number Theory Key

David Burton Elementary Number Theory Solutions Chapter 3 Primes And Their Distribution Exercise 3.2 Page 50 Problem 12 Answer

Given : pn is the nth prime number,

We have to establish each of the given statements: pn > 2n−1 for n ≥ 5.

Here,

The statement is correct for n = 5(p5 ⇒ 11>2⋅5−1 ⇒ 9).

Now,

If we consider that this statement is true for an arbitrary integer k > 5 and show that this statement is correct for k+1, then using the principle of induction we have that this statement is true for an arbitrary integer n ≥ 5.

Now,

If we assume that this statement is true for an arbitrary integer k > 5, then from the fact pk+1 − pk ≥ 2 (in other way if pk+1 = pk+1, then pk+1 is even)

Hence,

We get that

pk+1 ≥ pk + 2 > 2k−1 + 2 = 2(k+1)−1

Therefore,

pn > 2n−1 for n ≥ 5

Given : pn is the nth prime number,

We have to show that none of the integers

Pn = p1p2⋯pn + 1 is a perfect square.

We will show it by a contradiction.

Here,

Integer p2…pn is odd, so that exist an positive integer k such that p2…pn = 2k + 1,

Then we get that Pn is given of the form ​

Pn = 2(2k+1) + 1

= 4k + 3

Now,

If this integer is a perfect square, then exist an odd integer m = 2l + 1 (because Pn is odd)

such that Pn = m2.

Then we get next situation ​Pn = 4k + 3

= (2l+1)2

= 4l2 + 4l + 1

i.e. 4k + 2 = 4l2 + 4l

As we can see, 4 ∣ 4l2 + 4l but 4∤4k+1 which we have a contradiction.

Therefore,

None of the integers Pn = p1p2⋯pn+1 is a perfect square.

Given : pn is the nth prime number

We have to show that the sum \(\frac{1}{p_1}+\frac{1}{p_2}+\cdots+\frac{1}{p_n}\) is never an integer.

We will show it by a contradiction.

Here Let A = \(\frac{1}{p_1}+\frac{1}{p_2}+\cdots+\frac{1}{p_n}\).

Now,

Consider that A is an integer,

Then after multiplying it with p1p2…pn-1 we have that p1p2…pn-1A = p2p3…pn-1+p1p3…pn-1+…+p1p2…pn-2+ \(\frac{p_1 p_2 \cdots p_{n-1}}{p_n}\) is an integer.

Also

p1p2…pn-1A − p2p3…pn-1 − p1p3…pn-1−…−p1p2…pn-2 = \(\frac{p_1 p_2 \cdots p_{n-1}}{p_n}\) is an integer too.

Hence, pn ∣ p1p2…pn-1, then we have contradiction.

Therefore,

The sum \(\frac{1}{p_1}+\frac{1}{p_2}+\cdots+\frac{1}{p_n}\) is never an integer.

How To Solve Chapter 3 Exercise 3.2 Burton Number Theory

David Burton Elementary Number Theory Solutions Chapter 3 Primes And Their Distribution Exercise 3.2 Page 50 Problem 13 Answer

Given : n∣m

We have to show that Rn∣Rm

We will use above information.

Here,

We have, n∣m, then exists an integer k > 0 such that m = kn.

So, repunit Rm is given of the form :​

Rm = Rkn

= 11…1

= 10(k-1)nRn + 10(k-2)nRn+…+10nRn + Rn

Hence,

It is not hard to see that Rn ∣ Rm

Therefore,

If n ∣ m, then Rn ∣ Rm

Given : d ∣ Rn and d ∣ Rm

We have to show that d ∣ Rn+m

We will use above information.

Here,

We have, d ∣ Rn and d ∣ Rm, we need to show that d ∣ Rn+m.

Now,

Repunit Rm+n is given by : \(R_{m+n}=11 \ldots 1\)

= \(11 \ldots 1 \overbrace{00 \ldots 0}^n+\underbrace{1 \ldots 1}\)

= 10mRn + Rm

Hence,

It is not hard to see that d ∣ Rm+n.

Therefore,

If d ∣ Rn and d ∣ Rm, then d ∣ Rn+m

Given : gcd(n,m) = 1

We have to show that gcd(Rn,Rm) = 1

We will use above information.

Here,

We have, gcd(m,n) = 1 and m ≥ n.

Now,

By using Theorem 2.1. we have that m = kn + r for some integers 0 < k and 0 ≤ r < n.

Repunit Rm−n is given of the form :

Rm-n = Rm−10m-nRn

Hence,

It is not hard to conclude that gcd(Rm,Rn) = gcd(Rm-n,Rn).

If we repeat this procedure k times, we get that ​

gcd(Rm,Rn) = gcd(Rm-n,Rn)

= …

= gcd(Rm-kn,Rm)

= gcd(Rr,Rm)

Now, using Theorem 2.1. we get that n = k1r + r1 for some integers 0 < k−1 and 0 ≤ r1 < r.

Then using preceding procedure we get that ​gcd(Rm,Rn) = gcd(Rr,Rm)

= gcd(Rr,Rr1)

As we can see our procedure is based on Euclidean algorithm, so after using it several times, we obtain ​

gcd(Rm,Rn) = Rgcd(m,n)

= R1

= 1

Now,

If gcd(Rm,Rn) = 1,

then gcd(m,n) = 1.

If d = gcd(m,n),

then using result from part b) we have that Rd ∣ Rm and Rd ∣ Rn.

So, ​Rd ∣ gcd(Rm,Rn) = 1

⇒ d = 1

Therefore,

If gcd(n,m) = 1,

then gcd(Rn,Rm) = 1

Burton Number Theory Primes Exercise 3.2 Solutions

David Burton Elementary Number Theory Solutions Chapter 3 Primes And Their Distribution Exercise 3.2 Page 50 Problem 14 Answer

We have to obtain the prime factors of the repunit R10

We will use result : If n ∣ m, then Rn ∣ Rm

Here,

We have,  R2, R5 ∣ R10.

So, we repunit R10 is given of the form

R10 = R2⋅R5⋅k for some positive integer k.

Now,

From last result we get that K = \(\frac{R_{10}}{R_2 \cdot R_5}\)

= 9091

Integers 9091 and R2 = 11 are prime numbers,

So, we need to obtain the prime factors of R5 = 11111.

Prime factors of this number are 271 and 41.

Hence,

R10 = 11⋅41⋅271⋅9091

Therefore,

R10 = 11⋅41⋅271⋅9091

David Burton Elementary Number Theory Solutions Chapter 3 Primes And Their Distribution Exercise 3.1

David Burton Elementary Number Theory Solutions Chapter 3 Primes And Their Distribution

Page 43 Problem 1 Answer

Given ;There are infinitely many primes of the form n{2}−2

To find : Exhibit five such primes.

There are infinitely many primes of the form n2 − 2,

2 = 22 − 2

7 = 32 − 2

23 = 52 − 2

47 = 72 − 2

79 = 92 − 2

Hence the list of the prime number are of the given form n{2}−2. 2,7,23,47,79.

 

Page 43 Problem 2 Answer

Given ; Every positive integer can be written in the form p + a2, where p is either a prime or 1, and a ≥ 0.

To find : Give an example to show that the following conjecture is not true:

Here We will give an example to show that the following conjecture is not true:

Every positive integer can be written in the form p+a2, where p is either a prime or 1.

Take x = 25, hence 25

​= 0 + 25

= 21 + 4

= 9 + 16

= 16 + 9

But none of 0,4,9 and 16 is prime or 1

Hence we have shown that Every positive integer can be written in the form p + a{2} conjecture is not true: when x = 25

David Burton Elementary Number Theory Chapter 3 Exercise 3.1 Solutions

David Burton Elementary Number Theory Solutions Chapter 3 Primes And Their Distribution Exercise 3.1 Page 43 Problem 3 Answer

Given ; Any prime of the form 3n+1 is also of the form 6m+1

To find : Prove each of the assertions below:

here we know that If a = 3n + 1 ⟹ 3 ∤ a,a ≠ 2,

David Burton Elementary Number Theory Solutions Chapter 3 Primes And Their Distribution Exercise 3.1

so a is an odd prime not divisible by 3 .

By Division Algorithm, a = 6m + r,0 ≤ r < 6.

-​r ≠ 0,since if r = 0

⟹ a = 6m⟹3∣a

−r≠2, since if​ r = 2 ⟹ a

= 6m + 2 = 2(3m+1)

⟹ 2 ∣ a

– r≠3, since if ​r = 3 ⟹ a.

= 6m + 3

= 3(2m+1)

⟹ 3 ∣ a

– r ≠ 4, since if ​r = 4 ⟹ a

= 6m + 4

= 2(3m+2)

⟹ 2 ∣ a

– r ≠ 5, since if ​r = 5.

a = 6m + 5

= 3(2m+1) + 2

⟹ 2 ∣ a

So, r must be 1 .

Hence we have proved that if r = 1 Any prime of the 3n+1 form is also of the form 6m+1

Given ; Each integer of the form 3n+2 has a prime factor of this form.

To find : Prove each of the assertions below:

let a be the integer of the form 3n + 2,a = 3n + 2.

Let p be the prime factor of a, then p = 3r + 1 or 3r+2.

Assume that every prime factor of a has the form 3r+1,

then a also has the form 3r+1, since the product of two or more numbers of the form 3r+1 is also of the form 3r+1,

i.e (3m+1)(3n+1) = 9nm + 3m + 3n + 1 = 3(3nm+m+n) + 1

So, a must have at least one prime factor of the form 3n+2, if not, a can not be of the form 3n+2.

Hence we conclude that if, a must have at least one prime factor of the form 3n+2, if not, a can not be of the form 3n+2.

Given ; The only prime of the form n3−1 is 7

To prove the given of the assertions

We have n = 2

Therefore,​ 7 = 23 − 1

= 8 − 1

= 7

So, 7 is of the form n{3}−1.

Now for n > 2,n3 − 1 = (n−1)(n2+n+1)

Since, n > 2 ⟹ n−1 > 1 so (n−1)∣(n3−1).

Thus, n3−1 can not be a prime.

We conclude that n3−1 can not be a prime.

Given ; The only prime P for which 3p+1 is a perfect square is p = 5.

To find ; Prove each of the assertions below:

3.5 + 1 = 16 is a perfect square.

Now assume for prime p, 3p + 1 = a2, a ∈ z.

If a = 3k ⇒ 3p + 1 = 9k2.

9k2 – 3p = 3(3k2-p)

So, 3|1 a contradiction.

So a must be of the form 3k+1 or 3k+2.

Now 3p + 1 = a2

3p = a2 – 1

⇒ p = (a-1)(a+1)

If a = 3k+1

p = \(\frac{(a-1)(a+1)}{3}\)

= \(\frac{(3 k)(3 k+2)}{3}\)

p = k(3k+2) a contradiction, since p is prime.

If a = 3k+2

p = \(\frac{(a-1)(a+1)}{3}\)

= \(\frac{(3 k+1)(3 k+3)}{3}\)

p = (k+1)(3k+1). a contradiction, since p is prime. Thus 3p+1 cannot be a perfect square.

Hence we conclude that p=(k+1)(3k+1). a contradiction, since p is prime. Thus 3p+1 can not be a perfect square

Given ; The only prime of the form n2−4 is 5

To find ; Prove each of the assertions below:

5 = 32 – 5 = 5

So, 5 is of the form n{2}-4.

For n > 5, n2-4 > 0.

Since n > 3 ⇒ n2 – 4 = (n-2)(n+2).

So (n-2) > 1 and it is a factor of n{2} – 4,

So n2 – 4 can not be prime.

Hence we conclude that (n−2) > 1 and it is a factor of n2−4, so n2−4 can not be prime.

Solutions To Chapter 3 Exercise 3.1 Burton Number Theory

David Burton Elementary Number Theory Solutions Chapter 3 Primes And Their Distribution Exercise 3.1 Page 43 Problem 4 Answer

Given : If p ≥ 5 is a prime number,

To find ; show that p{2}+2 is composite.

But p on the form p = 3k + 1 or p = 3k + 2.

– If ​p = 3k + 1.

⟹ p−1 = 3k

⟹ 3∣(p−1)

⟹ 3∣(p−1)(p+1) + 3

So, 3∣(p2+2) ⟹ p2+2 is composite.

– If ​p = 3k + 2

⟹ p + 1

= 3(k+1)

⟹ 3∣(p+1)

⟹ 3∣(p−1)(p+1) + 3

So, 3∣(p2+2) ⟹ p2+2 is composite.

Hence we have proved that 3∣(p2+2) ⟹ p2+2 is composite.

 

Page 43 Problem 8 Answer

Given ; If p ≥ q ≥ 5 and p and q are both primes

To find ; prove that 24 ∣ p2−q2

Here we know p, q are odd primes. then they take one of these forms 3k+1 or 3k+2.

– If p = 3k+1 and q = 3m+1.

So ​p − q = 3(k−m).

⟹ 3∣(p−q)

⟹ 3∣(p−q)(p+q)

– If p = 3k+2 and q = 3m+2.

So ​p−q = 3(k−m).

⟹ 3∣(p−q)

⟹ 3∣(p−q)(p+q)

– If p = 3k+1 and q = 3m+2.

So​ p+q = 3(k+m)+3.

⟹ 3∣(p+q)

⟹ 3∣(p−q)(p+q)

Thus in all cases 3∣(p−q)(p+q) ⟹ 3∣p2−q2

Now since p, q are primes, they take one of these forms 4r+1 or 4s+3.

– If p = 4r+1 and q = 4s+1.

So p2−q2,

= 16r2 + 8r + 1 − 16r2 − 8s − 1 = 8(2r2+r−2s2−s)

so  8∣p2−q2

– If p = 4r+3 and q = 4s+3.

So p2 − q2 = 16r2 + 24r + 9 − 16r2 − 24s − 9 = 8(2r2+3r−2s2−3s),

so 8∣p2−q2

– If p = 4r + 1 and q = 4s + 3.

So ​p2 − q2 = 16r2 + 8r + 1 − 16r2 − 24s − 9

8(2r2+r−2s2−3s−1)

so 8∣p2−q2

Thus in all cases 8∣(p−q)(p+q) ⟹ 8∣p2 − q2⋯(1),(2)

From and since gcd(8,3) = 1 ⟹ 24∣p2−q2

Hence we have conclude that in all cases 8∣(p−q)(p+q) ⟹ 8∣p2−q2

From (1),(2) and since ​gcd(8,3) = 1

⟹ 24∣p2−q2

How To Solve Chapter 3 Exercise 3.1 Burton Number Theory

David Burton Elementary Number Theory Solutions Chapter 3 Primes And Their Distribution Exercise 3.1 Page 43 Problem 9 Answer

Given ; An unanswered question is whether there are infinitely many primes that are 1 more than a power of 2 , such as 5 = 2{2}+1

To find ; Find two more of these primes.

We have 5 = 2{2}+1

​17 = 24 + 1

and 257 = 28 + 1.

Hence we have found 2 more prime that are 17,257.

Given : A more general conjecture is that there exist infinitely many primes of the form n2 + 1; for example, 257 = 162 + 1

To find : Exhibit five more primes of this type.

Here put the value of n = 1, 2, 4, 6, 8 to find the prime number in the given form

we have ​n2+1;

257 = 162 + 1

​12 + 1 = 2

22 + 1 = 5

42 + 1 = 17

62 + 1 = 37

102 + 1 = 101

Hence we have found 5 more prime in the form of n{2}+1 that s are 2,5,17,37,101

 

Page 43 Problem 10 Answer

Given ; . If p ≠ 5 is an odd prime

To find : prove that either p2−1 or p2+1 is divisible by 10.

here we will put the value of r and try to find that the given integers are divisible by 10

we know that p is odd prime, then by Division Algorithm ​p = 10q + r,

r = 1,3,7,9

– If ​r = 1,.

p = 10q + 1

⟹ p2−1 = 100q2 + 20q

= 10(10q2+2q)

⟹ 10∣(p2−1)

– If ​r = 3,

p = 10q + 3

⟹ p2+1

= 100q2 + 60q + 10

​10(10q2+6q+1)

⟹ 10∣(p+−1)

– If ​r = 7,

p = 10q + 7

⟹ p2+1

= 100q2 + 140q + 50

​10(10q2+14q+5)

⟹ 10∣(p2+1).

– If ​r = 9,

p = 10q + 9

p2−1 = 100q2 + 180q + 80

= 10(10q2+18q+8)

⟹ 10∣(p2−1)

In all cases either 10∣(p2−1) or 10∣(p2+1)

Hence we conclude that In all cases either 10∣(p2−1) or 10∣(p2+1) is divisible by 10.

Solutions Guide For Chapter 3 Exercise 3.1 Burton Number Theory

David Burton Elementary Number Theory Solutions Chapter 3 Primes And Their Distribution Exercise 3.1 Page 43 Problem 12 Answer

Given; 1234, 10140 and 36000

To find the prime factorization of the given integers

The given integers are 1234, 10140, and 36000.

1234 = 2.617

10140 = 22.5.3.132

36000 = 25.53.32

The prime factorization of the given integer is:

1234 = 2⋅617

10140 = 22⋅5⋅3⋅132

36000 = 25⋅53⋅32

 

Page 43 Problem 13 Answer

Given : If n > 1 is an integer not of the form 6k+3

To find ; prove that n{2}+2{n} is composite.

here we will try to find in all the cases that the number is composite or not

By division we have ​n = 2k

n = 2k+1

– If n is even, n = 2k so, ​(2k)2 + 22k = 4k2 + 4k

⟹ 2∣n2 + 2n

Thus n2 + 2n is composite.

– If n is odd, then n = 6k+1 or n = 6k+5

– If n = 6k + 1

n ≡ 1​(3)

n2 ≡ 1​(3)

and 2 ≡ −1​(3)

2n ≡ −1​(3) (since n is odd )

So, n2 + 2n ≡ 0​(3)

Thus n2 + 2n is composite.

– If n = 6k + 5

n ≡ 2​(3)

n2 ≡ 4 ≡ 1​(3)

and 2 ≡ −1​(3)

2n ≡ −1​(3) (since n is odd )

So, n2 + 2n ≡ 0​(3)

Thus n2+2n is composite.

Therefore in all cases we have that n2 + 2n, is composite.

Hence we conclude that n2+2n is composite.

Therefore in all cases we have that n{2}+2{n}, is composite.

 

David Burton Elementary Number Theory Solutions Chapter 3 Primes And Their Distribution Exercise 3.1 Page 44 Problem 14 Answer

Given ; 6 = 29 − 23 = 137 − 131 = 599 − 593 = 1019 − 1013 = ⋯

To find : Express the integer 10 as the difference of two consecutive primes in 15 ways.

Here we will subtract 10 from all the given stes to find two consecutive numbers

We have 6 = 29 − 23 = 137 − 131 = 599 − 593 = 1019 − 1013 = ⋯

​10 = 23 − 13 = 149 − 139 = 191 − 181

= 41 − 31 = 251 − 241 = 293 − 283

= 47 − 37 = 347 − 337 = 419 − 409

= 71 − 61 = 431 − 421 = 557 − 547

= 83 − 73 = 701 − 691 = 113 − 103

Hence we have Express the integer 10 as the difference of two consecutive primes in 15 ways. is given by

10 = 23 − 13 = 149 − 139 = 191 − 181

= 41 − 31 = 251 − 241 = 293 − 283

= 47 − 37 = 347 − 337 = 419 − 409

= 71 − 61 = 431 − 421 = 557 − 547

= 83 − 73 = 701 − 691 = 113 − 103

 

Page 44 Problem 15 Answer

Given ; A square if and only if in the canonical form of a all the exponents of the primes are even integers

To find ; Prove that a positive integer a > 1 is square

pi is prime. So, a = k2 = (p1r1p2r2….psrs)2

= (p12r1p22r2….ps2rs)

So, all the exponents are even.

i.e a = (p12m1 p22m2….. ps2ms)

a = (p1m1 p2m2…..psms)2

So, a is a square

Hence we conclude that a = (p1m1p2m2⋯psms)2 So, a is a square.

 

David Burton Elementary Number Theory Solutions Chapter 3 Primes And Their Distribution Exercise 3.1 Page 44 Problem 16 Answer

Given ; An integer is said to be square-free if it is not divisible by the square of any integer greater than 1

To prove:

An integer n > 1 is square-free if and only if n can be factored into a product of distinct primes.

Assume n is square-free then for any a ∈ Z,a2∤n

Assume ​pr ∈ Z ∋ n = prp1p2⋯pn

r > 1 ⟹ r = 2 + s,s ≥ 0

Then \(\frac{n}{p^2}=\frac{p^{2+s} p_1 p_2 \cdots p_n}{p^2}\)

\(\frac{p^2 p^s p_1 p_2 \cdots p_n}{p^2}\)

which is a contradiction.

Thus r must equal 1.

Assume n is a product of distinct primes

n = p1p2⋯pn

Assume ∃ a ∈ Z ∋ a2 ∣ n since a2 is square then a2 = q12r1q22r2⋯qs2rs contradiction

Hence we conclude that if n is a product of distinct primes n = p1p2⋯pn assume ∃ a ∈ Z ∋ a2 ∣ n since a2 is square then a2 = q12r1q22r2⋯qs2rs contradiction

Given ; An integer is said to be square-free if it is not divisible by the square of any integer greater than 1

To find ; Every integer n > 1 is the product of a square-free integer and a perfect square.

Here we have ​n = q12r1q22r2⋯qs2rs

,ri = 2pi + ri,

r = 0,1

​n = q12p1+r1q22p2+r2⋯qs2ps+rs

= (q1r1q2r2⋯qsrs)(q1p1q2p2⋯qsps)2

​Thus every integer is a product of a square free and a perfect square.

Hence we conclude that every integer is a product of a square free and a perfect square

Exercise 3.1 Burton Elementary Number Theory Problem Walkthrough

Page 44 Problem 17 Answer

Given ; k ≥ 0 and m is an odd integer.

To find ; Verify that any integer n can be expressed as n = 2{k}m

here we will find whether m is odd or even if its odd then n = \(\prod_{i=1}^r p_i^{\alpha_i}=2^0 \prod_{i=1}^r p_i^{\alpha_i}=2^0 m\)

We know that by Fundamental theorem of Arithmetics

n = p1α​1p2α​s⋯psα​s, either n is even or n is odd.

– If n is even then 2∣n or ∃ pj = 2 ∋ 1 ≤ i ≤ r

⇒ n = 2αj \(\prod_{i=1, i \neq j}^r p_i^{\alpha_i}\)

Thus, n = 2αjm (where m = \(\prod_{i=1, i \neq j}^r p_i^{\alpha_i}\) is odd.)

-If n is odd, then n = \(\prod_{i=1}^r p_i^{\alpha_i}\)

= [/latex]2^0 \prod_{i=1}^r p_i^{\alpha_i}[/latex]

= 20m

(where m = \(\prod_{i=1}^r p_i^{\alpha_i}\) is odd)

Hence we conclude that If n is odd, then

n = \(\prod_{i=1}^r p_i^{\alpha_i}=2^0 \prod_{i=1}^r p_i^{\alpha_i}=2^0 m\)

(where m = \(\prod_{i=1}^r p_i^{\alpha_i}\) is odd)

 

David Burton Elementary Number Theory Solutions Chapter 3 Primes And Their Distribution Exercise 3.1 Page 44 Problem 18 Answer

Given ; Numerical evidence makes it plausible that there are infinitely many primes p such that is also prime. p + 50

To find ; List 15 of these primes.

we will start with 3 as a prime number and add 50 to get desired solution

we have prime p such that p + 50 is also a prime

​(3,53)       (47,97)       (107,157)    (11,61)       (47,97)

(17,67)     (17,67)       (23,73)       (29,79)       (53,103)

(59,109)   (83,133)    (101,151)   (107,157)   (113,163)

Hence all the 15 prime number in the form p such that p + 50

(3,53)       (47,97)       (107,157)    (11,61)       (47,97)

(17,67)     (17,67)       (23,73)       (29,79)       (53,103)

(59,109)   (83,133)    (101,151)   (107,157)   (113,163)

 

Page 44 Problem 19 Answer

Given ; A positive integer n is called square-full, or powerful, if p2 ∣ n or every prime factor p of n , if n is square full

To find ; show that it can be written in the form n = a2b3, with a and b positive integers.

here we will show first whether km​i are odd (so kmi ≥ 3). and kn are even,

let n = p1k1⋯ prkr since n is square full, ki ≥ 2.

\(p_1^{k_1} \cdots p_r^{k_r}=q_{m_1}^{k_{m 1}} \cdots q_{m_s}^{k_{m s}} q_{n_1}^{k_{n 1}} \cdots q_{n_t}^{k_{t t}}\)

Where kmi are odd (so kmi ≥ 3). and kni are even,

so kni = 2vi

​n = \(q_{m_1}^{k_{m 1}} \cdots q_{m_s}^{k_{m s}}\left(q_{n_1}^{v_1} \cdots q_{n_t}^{v_t}\right)\)
​​

​= \(q_{m_1}^{k_{m 1}} \cdots q_{m_s}^{k_{m s}}\left(q_{n_1}^{v_1} \cdots q_{n_t}^{v_t}\right)^2\)

= \(q_{m_1}^{k_{m 1}} \cdots q_{m_s}^{k_{m s}}(g)^2, where g = (\left(q_{n_1}^{v_1} \cdots q_{n_t}^{v_t}\right))\)

since kmi is odd and ≥ 3, so kmi−3 is even.

n = \(q_{m_1}^3 \cdots q_{m_s}^3\left(q_{m_1}^{m-3} \cdots q_{m_s}^{m-3}\right)\left(g^2\right)\)

Let ​mi−3 = 2wi,

qm1⋯qms = b

∴ n = \(b^3\left(q_{m_1}^{2 w_1} \cdots q_m^{2 w_s}\right)\left(g^2\right)\)

Let f = \(q_{m_1}^{w_1} \cdots q_{m_s}^{w_s}\)

then n = b3f2g2

Let a = fg, then, n = a2b3

Hence we conclude that if kmi is odd and ≥ 3,so kmi − 3 is even.

n = \(q_{m_1}^3 \cdots q_{m_s}^3\left(q_{m_1}^{m-3} \cdots q_{m_s}^{m-3}\right)\left(g^2\right)\)

​mi − 3 = 2wi,

qm1⋯qms = b

∴ n = \(b^3\left(q_{m_1}^{2 w_1} \cdots q_m^{2 w_s}\right)\left(g^2\right)\)

f = \(q_{m_1}^{w_1} \cdots q_{m_s}^{w_s}\)

then n = b3f2g2

a = fg, then, n = a{2}b{3}

Hence proved

David Burton Elementary Number Theory Solutions Chapter 2 Divisibility Theory In The Integers Exercise 2.3

David Burton Elementary Number Theory Solutions Chapter 2 Divisibility Theory In The Integers

Page 24 Problem 1 Answer

Here ,we have to show that (-a)|b, a|(-b), and (-a)|(-b)

Let a∣b then ∃ c ∋ a⋅c = b

⟹ a⋅c = (−a)⋅(−c) = b ⟹ (−a)∣b

⟹ −(a⋅c) = −b = a⋅(−c) ⟹ a∣(−b)

⟹ −(a⋅c) = −b = (−a)⋅c ⇒ (−a)∣(−b)

Thus, we show that (−a)∣b, a∣(−b), and (−a)∣(−b).

David Burton Elementary Number Theory Chapter 2 Exercise 2.3 Solutions

Page 24 Problem 2 Answer

Here, we have to verify that if a∣b then a∣bc

Let a∣b then ∃x ∋ a⋅x = b

∴ ac = bc ⟹ a ∣ bc

Thus, we verified that if a ∣ b, then a ∣ bc

Here, we have to verify that if a∣b and a∣c then a2∣ bc

Let a∣b and a∣c then, ∃ x,y ∋ ax = b,ay = c

∴ (ax)(ay) = bc = a2xy ⟹ a2 ∣ bc

Thus, we verified that if a∣b and a∣c, then a2 ∣ bc

David Burton Elementary Number Theory Solutions Chapter 2 Divisibility Theory In The Integers Exercise 2.3

Here, we have to verify that a∣b if and only if ac ∣ bc, where c ≠ 0

Let a∣b then ∃ x ∋ ax = b,

∴ acx = bc = a2xy ⟹ ac ∣ bc

Now, let ac ∣ bc then ∃ x ∋ acx = bc

Since, c ≠ 0 ∴ ax = b ⟹ a ∣ b

Thus, we verified that a∣b if and only if ac ∣ bc, where c ≠ 0

Here, we have to verify that if a ∣ b and c ∣ d, then ac ∣ bd

Let a∣b and c∣d then, ∃ x, y ∋ ax = b,cy = d

∴ (ax)(cy) = ac(xy) = bd ⟹ ac ∣ bd.

Thus, we verified that a ∣ b and c ∣ d then, ac ∣ bd

 

David Burton Elementary Number Theory Solutions Chapter 2 Divisibility Theory In The Integers Exercise 2.3 Page 24 Problem 4 Answer

Here, we have to use mathematical induction to establish the divisibility statements, 8∣52n + 7.It’s given that 52(k+1) + 7 = 52(52k+7) + (7−52⋅7).

For n = 1:52n + 7 = 25 + 7 = 32 and 8 ∣ 32.Suppose it’s true for n = k then we want to prove it for n = k + 1.

Let 8 ∣ 52k + 7 ∴ ∃ x ∋ 8x = 52k + 7

Now, for n = k + 1

​52(k+1) + 7 = 52⋅52k + 7

= 52(52k+7) − 52⋅7 + 7

= 52(8x) − 52 − 7(52−1)

= 52(8x) − 7(24)

= 8x(25) − 8(7⋅3)

= 8(25x−21)

∴ 8 ∣ 5k+1

Thus, by mathematical induction for n ≥ 1,8 ∣ 5n

Thus, we have to use mathematical induction to establish the divisibility statements 8 ∣ 52n + 7

Here, we have to use mathematical induction to establish the divisibility statements, 15 ∣ 24n − 1

For, n = 1 : 24 − 1 = 16 − 1 = 15 and 15 ∣ 15.Suppose it’s true for n = k then we want to prove it for n = k + 1.

Let 15 ∣ (24k−1) ∴ ∃ x ∋ 15x = 24k − 1

Now, for n = k + 1

24(k+1) − 1 = 24⋅24k − 1 + 24 − 24

= 24(24k−1) + (24−1)

= 24(15x) + 15

= 15(x24+1)

∴ 15 ∣ 24(k+1) − 1

Thus, by mathematical induction for n ≥ 1,15 ∣ 24n − 1

Thus, we use mathematical induction to establish the divisibility statements, 15 ∣ 24n − 1

Here, we have to use mathematical induction to establish the divisibility statements, 5 ∣ 33n+1 + 2n+1

For n = 1 : 33+1 + 22 = 81 + 4 = 85 and 5 ∣ 85. Suppose it’s true for n = k then we want to prove it for n=k+1.

Let 5 ∣(33k+1 + 2k+1) ∴ ∃ x ∋ 5x = 33k+1 + 2k+1

Now for n = k + 1

33(k+1)+1 − 2k+2 = 33k+4 − 2k+2

= 33⋅33k+1 + 2⋅2k+1 + 3⋅2k+1 − 33⋅2k+1

= 33(33k+1 + 2k+1) − 2k+1(33−2)

= 33(5x) − 2k+1(25)

= 5(x33 − 5⋅2k+1)

∴ 5 ∣ (33n+1 + 2n+1)

Thus, by mathematical induction for n ≥ 1, 5 ∣ 24n − 1

Thus, we use mathematical induction to establish the divisibility statements, 5 ∣ 24n−1

Here, we have to use mathematical induction to establish the divisibility statements, 21 ∣ 4n+1 + 52n-1

For ,n = 1: 42 + 51 = 21 and 21 ∣ 21.Suppose, it’s true for n = k then we want to prove it for n = k + 1.

Let 21 ∣ (4k+1+52k-1) ∴ ∃ x ∋ 21x = 4k+1 + 52k-1

Now, for n = k + 1

​43(k+2) − 52(k+1)−1 = 4k+2 − 52k+1

= 4⋅4k+1 + 52⋅52k-1 + 4⋅52k-1− 4⋅52k-1

= 4(4k+1 + 52k-1) + 21(52k-1)

= 4(21x) + 21(52k-1)

= 21(4x+52k-1)

∴ 21 ∣ (4(k+1)+1 + 52(k+1)-1)

Thus, by mathematical induction for n ≥ 1, 21∣(4k+1 + 52k+1)

Thus, we use mathematical induction to establish the divisibility statements, 21 ∣ 4n+1 + 52n-1

Here, we have to use mathematical induction to establish the divisibility statements, 24 ∣ 2⋅7n + 3⋅5n−5

Now we want to prove by mathematical induction that 24 ∣ 4⋅7k + 20 for s = 1: 4⋅71 + 20 = 48 and 24 ∣ 48

Suppose it’s true for k = s then we want to prove it for k=s+1

Let 24 ∣ 4⋅7s + 20 ∴ ∃ x ∋ 24x = 4⋅7s + 20

Now, for n = k + 1

​4⋅7s+1 + 20 = 7(4⋅7s)+20

= 7(4⋅7s+20) + 20 − 140

= 7(24y) − 24⋅5

∴ ∃ q ∋ 24q = 4⋅7k + 20

∴ eq (1) = 5(24x) + 24q

Thus, by mathematical induction for n ≥ 1,24 ∣ 2⋅7n + 3⋅5n−5

Thus, we use mathematical induction to establish the divisibility statements, 24 ∣ 2⋅7n + 3⋅5n−5

Solutions To Chapter 2 Exercise 2.3 Burton Number Theory

David Burton Elementary Number Theory Solutions Chapter 2 Divisibility Theory In The Integers Exercise 2.3 Page 24 Problem 5 Answer

Here, we have to prove that for any integer a one of the integers a,a+2,a+4 is divisible by 3

From the division algorithm, we know that every a is on the form 3q, 3q+1 or 3q+2

Case 1: Suppose a = 3q, then a is divisible by 3

Case 2: Suppose a = 3q + 1,then a + 4 = 3q + 6 = 3(q+2),then a+2 is divisible by 3

Case 3: Suppose a = 3q + 2,then a+4 = 3q + 6 = 3(q+2).Thus a+1 is divisible by 3

therefore for any integer a,any of the forms a,a+2 or a+4 is divisible by 3

Thus, we prove that for any integer a one of the integers a, a+2, a+4 is divisible by 3

 

Page 25 Problem 6 Answer

Here, we have to verify that 2∣a(a+1), and 3∣a(a+1)(a+2)

According to the division algorithm, every a is of the form 2q or 2q+1

Case 1: If a = 2q then a + 1 = 2q + 1, since a is even ⟹ 2∣a ⟹ 2∣a(a+1)

Case 2 : If a = 2q + 1 then

a + 1 = 2q + 2 = 2(q+1), since a + 1 is even ⟹ 2∣a+1 ⟹ 2∣a(a+1)

According to division algorithm, every a is of the form 3q,3q+1 or 3q+2

Case 1 : If a = 3q then

3∣a ⟹ 3∣a(a+1)(a+2)

Case 2 : If a = 3q + 1 then,

a + 2 = 3q + 3 = 3(q+1),thus

3 ∣a + 2 ⟹ 3∣a(a+1)(a+2)

Case 3: If a = 3q + 2,then

a + 1 = 3q + 3 = 3(q+1),thus

3∣a + 1 ⟹ 3∣a(a+1)(a+2)

Thus, we verify that 2∣a(a+1), and 3∣a(a+1)(a+2).

Here, we have to verify that 3∣a(2a2+7)

According to the division algorithm, every a is of the form, 3q,3q+1, or 3q+2

Case 1 : If a = 3q then,3 ∣ a ⟹ 3∣a(2a2+7)

Case 2: If a = 3q + 1 then, a2 = 9q2 + 6q + 1, ​

​⟹ 2a2 + 7 = 2(9q2+6q+1) + 7

= 18q2 + 12q + 9 = 3(6q2+4q+3)

thus 3∣∣2a2 + 7 ⟹ 3∣∣a(2a2+7)

Case 3: If a = 3q + 2 then, a2 = 9q2 + 12q + 4, ​

​⟹ 2a2 + 7 = 2(9q2+12q+4) + 7

= 18q2 + 24q + 15 = 3(6q2+8q+5)

Thus 3 ∣ 2a2 + 7 ⟹ 3 ∣ a(2a2+7)

Thus, we verified 3 ∣ a(2a2+7)

Here, we have to verify that if a is odd ,then 32 ∣ (a2+3)(a2+7)

According to the division algorithm, every a is in the form 4q + r​ ∋ 0 ≤ r ≤ 3. But a is odd then the only possible forms of a are 4q+1 or 4q+3

Case 1 : If a = 4q + 1, then a2 = 16q2 + 8q + 1

⟹ a2 + 3 = 16q2 + 8q + 4 = 4(4q2+2q+1)​⋯(1)

a2 + 7 = 16q2 + 8q + 8 = 8(2q2+q+1)​⋯(2)

From (1) and (2)

(a2+3)(a2+7) = [4(4q2+2q+1)][8(2q2+q+1)]

​= 32(4q2+2q+1)(2q2+q+1)

Thus 32 ∣ (a2+3)(a2+7)

Case 2 : If a a = 4q + 3 then,

a2 = 16q2 + 24q + 9

​⟹ a2 + 3 = 16q2 + 24q + 12 = 4(4q2+6q+3)​⋯(1)

a2 + 7 = 16q2 + 24q + 16 = 8(2q2+3q+2)​⋯(2)

from (1) and (2)

(a2+3)(a2+7) = [4(4q2+6q+3)][8(2q2+3q+2)]

​= 32(4q2+6q+3)(2q2+3q+2)

Thus 32 ∣ (a2+3)(a2+7)

Thus, we verified if a is odd ,then 32∣(a2+3)(a2+7)

 

Page 25 Problem 7 Answer

Here, we have to prove that if a and b are both odd integers, then 16 ∣ a4 + b4 − 2

Since a and b are both odd integers then a = 2r + 1 and b = 2s + 1 where k, l ∈ Z.

Now,

a4 + b4 – 2 = (2r+1)4 + (2s+1)4 – 2

= \(\left(\begin{array}{l}
4 \\
0
\end{array}\right)(2 r)^4+\left(\begin{array}{l}
4 \\
1
\end{array}\right)(2 r)^3+\left(\begin{array}{l}
4 \\
2
\end{array}\right)(2 r)^2+\left(\begin{array}{l}
4 \\
3
\end{array}\right)(2 r)+1\)

+\(\left(\begin{array}{l}
4 \\
0
\end{array}\right)(2 s)^4+\left(\begin{array}{l}
4 \\
1
\end{array}\right)(2 s)^3+\left(\begin{array}{l}
4 \\
2
\end{array}\right)(2 s)^2+\left(\begin{array}{l}
4 \\
3
\end{array}\right)(2 s)+1-2\)

= 16(r4+s4) + 32(r3+s3) + 24r2 + 8r + 24s2 + 8s

to prove that 16 ∣ a4 + b4 − 2 we just need 16 ∣ 24r2 + 8r

If r is odd then r = 2k + 1,then

​24(2k+1)2 + 8(2k+1)

= 96k2 + 96k + 24 + 16k + 8

= 96k2 + 96k + 16k + 32

= 16(8k2+8k+k+2)

If r is even then r = 2k,thus

24(2k)2 + 8(2k) = 96k2 + 16k = 16(8k2+k)

Thus, 16 ∣ 24r2 + 8r, similarly 16 ∣ 24s2 + 8s

∴ 16 ∣ a4 + b4 − 2

Thus, we prove that if a and b are both odd integers, then 16 ∣ a4 + b4 − 2

Divisibility Theory Exercise 2.3 Answers David Burton

David Burton Elementary Number Theory Solutions Chapter 2 Divisibility Theory In The Integers Exercise 2.3 Page 25 Problem 8 Answer

Here, we have to prove that the sum of the squares of two odd integers cannot be a perfect square.

Let a and b be odd integers, then a = 2r + 1 and b = 2s + 1 for some r, s ∈ Z.

Now,

a2 + b2 = (2r+1)2 + (2s+1)2 = 4r2 + 4r + 1 + 4s2 + 4s + 1 = 4(r2+s2+r+s) + 2 = 4k + 2

where, k = r2 + s2 + r + s

Suppose a2 + b2 is a perfect square, then a2 + b2 = c2 = 4k + 2 = 2(2k+1)

Then c2 is even ⇒ c is even, so c = 2m ⟹ c2 = 4m2 = 4l where l = m2

Thus, a2 + b2 = c2 ⟹ 4k + 2 = 4l,this contradict the uniqueness of division algorithm, ∴ a2 + b2 ≠ c2 if a, b are odd

Thus, we proved that the sum of the squares of two odd integers cannot be a perfect square.

We have to prove that the product of four consecutive integers is 1 less than a perfect square.

Consider the four consecutive integers be k, k+1, k+2 and k+3

The product of these integers will be,

k(k+3)(k+1)(k+2) = (k2+3k)(k2+3k+2)

=((k2+3k+1)−1)((k2+3k+1)+1)

= (k2+3k+1)2 − 12

Now let​(k2+3k+1) = p where p is some integer.

Hence (k2+3k+1)2 = p2

Therefore we have,

k(k+3)(k+1)(k+2) = p2 − 1

Hence we have proved that the product of four consecutive integers is 1 less than a perfect square.

 

Page 25 Problem 9 Answer

We have to establish that the difference of two consecutive cubes is never divisible by 2.

Consider the two consecutive numbers be a and a+1

Here ∤ symbolize does not divide and ∣ means does divide.

We have to prove 2 ∤ (a+1)3 − a3

Solving (a+1)3 − a3 we get,

(a+1)3 − a3 = a3 + 3a2 + 3a + 1 − a3

= 3a2 + 3a + 1

= 3a(a+1) + 1

Now,

if a is even then,

2 ∣ a

⇒ 2 ∣ a(a+1)

if a is odd, then a+1 is even, then,

2 ∣ a + 1

⇒ 2 ∣ a(a+1)

So 2 ∣ a(a+1)

Therefore,

x ∈ Z, 2x = a(a+1)

Thus,

3a(a+1) + 1 = 3(2x)+1

= 2(3x) + 1

which is odd.

Hence 2∤(a+1)3 − a3.

Hence we have proved that 2 ∤ (a+1)3 − a3.

 

Page 25 Problem 10 Answer

We have to show that

gcd(a,0) = ∣a∣

gcd(a,a) = ∣a∣

gcd(a,1) = 1

Sincea∣0 and a∣a,then ∣a∣ is a common divisor of a and 0.

Now, let b be another common divisor of a,0.

Then,

b ∣ a

⇒ ∣b∣ ≤ ∣a∣

Thus ∣a∣ is the greatest common divisor of a and 0.

Since a∣a, then ∣a∣ is a common divisor of a. Now, let b be another common divisor of a and a.

Then,

b ∣ a

⇒ ∣b∣ ≤ ∣a∣

Thus ∣a∣ is the greatest common divisor of a and a.

Since 1∣a and 1∣1,then 1 is a common divisor of a and 1.

Now, let b be another common divisor of a,1.

Then,

b ∣ 1

⇒ ∣b∣ ≤ 1

Thus 1 is the greatest common divisor of a and 1.

Hence we have proved that,

​gcd(a,0) = ∣a∣

gcd(a,a) = ∣a∣

gcd(a,1) = 1

Burton Number Theory Divisibility Exercise 2.3 Solutions

David Burton Elementary Number Theory Solutions Chapter 2 Divisibility Theory In The Integers Exercise 2.3 Page 25 Problem 12 Answer

We have to prove that, for a positive integer n and any integer a, gcd(a,a+n) divides n and hence,gcd(a,a+1) = 1

Here a|b means a divides b

Let gcd(a,a+1) = d, then d|a and d|a+n

But we know that gcd(a, a+n) divides any linear combination of a and a+n.

Thus

d|(a+n) – a

⇒ d|n

Now, let gcd(a, a+1) = t

Therefore,

t|a + 1 – a

⇒ t|a

⇒ t ≤ 1

⇒ t = 1

Hence we have proved that for a positive integer n and any integer a,gcd(a,a+n) divides n and hence,gcd(a,a+1) = 1

 

Page 25 Problem 13 Answer

We are given integers a and b.

We have to prove that there exist integers x and y for which c = ax + by if and only ifgcd(a,b)∣c.

Let us assume c = ax + by,

Now let gcd(a,b) = d,

then d∣a and d∣b

thus there exists,

​t,l in Z

a = dt

b = dl

Therefore,

c = ax + by

= dtx + dly

= d(tx+ly)

d∣c

Hence we have proved that there exist integers x and y for which c = ax + by if and only if gcd(a,b)∣c.

Given: Integers a and b, we have to prove:

If there exists integers x and y for which ax + by = gcd(a,b), then gcd(x,y) = 1

Let us assume gcd(a,b)∣c and let gcd(a,b) = d.

This implies c = fd for some f∈Z.

Then, ∃ s,r ∈ Z∋.

d = sa + rb

This implies:

c = fd

= f(sa+rb)

= (fs)a + (fr)b

= xa + yb

Where, ​x = fs

y = fr

Proved that if there exists integers x and y for which ax + by = gcd(a,b), then gcd(x,y) = 1.

 

Page 25 Problem 15 Answer

We are given thata and b are integers, not both of which are zero.

We have to prove that gcd(2a−3b,4a−5b) divides b and hence,gcd(2a+3,4a+5) = 1

We have,

−2(2a−3b) + (4a−5b) = −4a + 6b + 4a − 5b

−2(2a−3b) + (4a−5b) = b

Thus gcd(2a−3b,4a−5b) ∣ b.

Since​ 2(2a+3)−(4a+5) = 4a + 6 − 4a − 5

= 1

Thus gcd(2a+3,4a+5) ∣ 1 ⟹ gcd(2a+3,4a+5) = 1

Hence we have proved that gcd(2a−3b,4a−5b) divides b and hence,gcd(2a+3,4a+5) = 1

 

David Burton Elementary Number Theory Solutions Chapter 2 Divisibility Theory In The Integers Exercise 2.3 Page 25 Problem 17 Answer

We have to prove that the expression(3n)!/(3!)2 is an integer for all n ≥ 0.

For n = 1, we have,

\(\frac{(3 \cdot 1) !}{(3 !)^1}=\frac{6}{6}\)

Hence the result is true for n = 1

Now let us assume that the result is true for n = k we have,

\(\frac{(3 \cdot 1) !}{(3 !)^1}\) = l, l is any integer

Now we have to prove that the result is true for n = k + 1

we have,

\(\frac{(3(k+1)) !}{(3 !)^{k+1}}=\frac{(3 k+3) !}{(3 !)^k(3 !)}\)

= \(\frac{(3 k) !}{(3 !)^k} \cdot \frac{(3 k+3)(3 k+2)(3 k+1)}{6}\)

= \(l \cdot \frac{(k+1)(3 k+2)(3 k+1)}{2}\)

Now,

If k is even then,

k = 2r

⇒ 3k + 2 = 6r + 2

= 2(3r+1)

and hence 2 ∣ 3k + 2

If k is odd then,

k = 2r + 1

⇒ k + 1 = 2r + 2

= 2(r+1)

and hence 2∣k + 1

Therefore we conclude \(\frac{(k+1)(3 k+2)(3 k+1)}{2}\) is an integer, therefore \(\frac{(3(k+1)) !}{(3 !)^{k+1}}\) is an integer.

So by mathematical induction we have, (3n)!/(3!)n is an integer for all n ≥ 0.

We have proved that the expression(3n)!/(3!)​n is an integer for all n ≥ 0.

 

Page 25 Problem 18 Answer

We are given a statement,

The product of any three consecutive integers is divisible by 6.

We have to prove the above statement.

Here a|b means a divides b

Let the three consecutive integers be

n, (n+1), (n+2).

Since 6 = 2.3 and gcd(2,3) = 1

If n is even, then,

2|n

⇒ 2|n(n+1)(n+2)

If n is odd, then n+1 is even and hence,

2|(n+1)

⇒ 2|n(n+1)(n+2)

Now, by division algorithm, n = 3k+r, 0 ≤ r < 3.

If n = 3k + 1, then,

n+2 = 3k+3

= 3(k+1)

and thus

3|(n+1)

⇒ 3|n(n+1)(n+2)

If n – 3k + 2, then

n+1 = 3k+3

= 3(k+1)

and thus

3|(n+1)

⇒ 3|n(n+1)(n+2)

Therefore we have

2|n(n+1)(n+2) and 3|n(n+1)(n+2), thus 6|n(n+1)(n+2)

We have proved that the product of any three consecutive integers is divisible by 6.

Elementary Number Theory Burton Chapter 2 Exercise 2.3 Explanations

David Burton Elementary Number Theory Solutions Chapter 2 Divisibility Theory In The Integers Exercise 2.3 Page 25 Problem 19 Answer

We are given,

If a is an arbitrary integer, then 6 ∣ a(a2+11).

We have to establish the given assertion.

By division algorithm, a = 6q + r, 0 ≤ r < 6

If r = 0,

​⟹ a = 6q

⟹ 6∣a

So, 6∣a(a2+11).

If r = 1,


​⟹ a = 6q + 1

⟹ (a2+11) = 36q2 + 12q + 12

= 6(6q2+2q+2)

So, 6∣(a2+11)

⟹ 6∣a(a2+11)

If r = 2

​⟹ a = 6q + 2

= 2(3q+1)

So,

2∣a and (a2+11)

(a2+11) = 36q2 + 24q + 15

= 3(12q2+8q+5)

So, 3∣(a2+11)⟹6∣a(a2+11)

⟹ 6a(a2+11)

If r = 3

​⟹ a = 6q + 3

= 3(2q+1)

So, 3∣a

(a2+11) = 36q2 + 36q + 20

(a2+11) = 2(18q2+18q+10)

So,

2∣(a2+11) ⟹ 6∣a(a2+11)

If r = 4

​​⟹ a = 6q + 4

= 2(3q+2)

So,

2∣a and (a2+11)

(a2+11) = 36q2 + 24q + 27

= 3(12q2+8q+9)

So, 3∣(a2+11) ⟹ 6∣a(a2+11)

⟹ 6a(a2+11)

If r = 5,

​⇒ a = 6q + 5

⇒ (a2+11) = 36q2 + 60q + 36

= 6(6q2+10q+6)

So, 6∣(a2+11)

⇒ 6 ∣ a(a2+11)

Therefore in all cases 6 ∣ a(a2+11)

We have proved that if a is an arbitrary integer, then 6∣a(a2+11).

We are given,

If a is an order integer, then 24 ∣ a(a2−1)

We have to establish the given assertion.

Since a is odd then a is in the form

a = 4k + 1 or

a = 4k + 3

= 4k−1.

Let​ a = 4k + 1

⟹ a2 = 16k2 + 8k + 1

= 8(2k2+k) + 1

so, a2= 8m + 1 where

m = 2k2 + k.

Thus,​a(a2−1) = (4k+1)(8m+1)

= 32km+8m

= 8(4km+m).

So 8∣a(a2−1)​⋯(1)

Similarly if a = 4k−1,k ∈ Z.

If r = 0

​⇒ 3∣a

⇒ 3∣a(a2−1).

If r = 1

​⇒ a = 3q + 1

⇒ a2 − 1 = 9q2 + 6q

= 3(3q2+2q).

So,​3∣(a2−1)

⟹ 3a(a2−1)

If r = 2

​⟹ a = 3q + 2

⟹ a2−1 = 9q2 + 12q + 3

= 3(3q2+4q+1).

So,​ 3∣(a2−1)

⟹ 3a(a2−1)

Since,

gcd(8,3) = 1

24 ∣ a(a2−1)

We have proved that If a is an odd integer, then 24|a(a2-1).

We are given that a and b are odd integers.

We have to prove that 8∣(a2−b2)

Assuming that a,b are odd integers, then we have three cases,

If ​a = 4k+1

b = 4m+1

then,

a2−b2 = (16k2+8k+1)−(16m2+8m+1)

= 16(k2−m2)+8(k−m)

= 8(2(k2−m2)+(k−m)).

Hence 8∣a2−b2

If​ a = 4k−1

b = 4m−1

then,

a2−b2 = (16k2−8k+1)−(16m2−8m+1)

= 16(k2−m2)−8(k−m)

= 8(2(k2−m2)−(k−m))

Hence 8∣a2−b2

If​ a = 4k−1

b = 4m + 1

then,

a2 − b2 = (16k2−8k+1) − (16m2+8m+1)

= 16(k2−m2) + 8(k+m)

= 8(2(k2−m2) + (k+m)).

Hence 8∣a2−b2

Therefore we conclude that 8∣a2−b2

We have proved that if a and b are odd integers, then 8∣(a2−b2)

We are given an assertion,

If a is an integer not divisible by 2 or 3, then 24∣(a2+23).

We have to prove the assertion.

As a is not divisible by 2, then a is odd. Thus a=4k+1 or 4k−1

Since a is not divisible by 3,Thus a = 3q + 1 or 3q + 2

Therefore we have four cases.

Case 1

If​ a = 4k + 1

= 3q + 1

So,

(a2+23) = (16k2+8k+24)

(a2+23) = 8(2k2+k+3)

Thus 8∣(a2+23)…(1)

Also,

(a2+23) = 9q2 + 6q + 24

(a2+23) = 3(3q3+2q+8)

Thus 3∣(a2+23)…(2)

Therefore from(1) and (2) we have, 24∣(a2+23)

Case 2

If​ a = 4k−1

= 3q + 2

So,

(a2+23) = (16k2−8k+24)

= 8(2k2−k+3).

Thus 8∣(a2+23)…(1)

Also,

(a2+23) = 9q2 + 12q + 27

(a2+23) = 3(3q3+4q+9)

Thus 3∣(a2+23)…(2)

Therefore from(1) and (2) we have, 24∣(a2+23)

Case 3

If a = 4k + 1

= 3q + 2

So,

(a2+23) = (16k2+8k+24)

(a2+23) = 8(2k2+k+3)

Thus 8∣(a2+23)…(1)

Also,

(a2+23) = 9q2 + 12q + 27

(a2+23) = 3(3q3+4q+9)

Thus 3∣(a2+23)…(2)

Therefore from(1) and (2) we have,

24∣(a2+23)

Case 4

If ​a = 4k − 1

= 3q + 1

So,

(a2+23) = (16k2−8k+24)

= 8(2k2−k+3).

Thus 8∣(a2+23)…(1)

Also,

(a2+23) = 9q2 + 6q + 24

(a2+23) = 3(3q2+2q+8)

Thus 3∣(a2+23)…(2)

Therefore from(1) and (2) we have,

24∣(a2+23)

Therefore we conclude that 24∣(a2+23)

Hence we have proved that if a is an integer not divisible by 2 or 3, then 24∣(a2+23).

We have to prove that if a is an arbitrary integer, then 360∣a2(a2−1)(a2−4).

We have,

a2(a2−1)(a2−4) = a2(a+1)(a−1)(a+2)(a−2)

= (a−2)(a−1)(a)(a+1)(a+2)(a)

Also 360 = 5 × 9 × 8 where5,8,9 are relatively prime.

Now we know that(a−2)(a−1)(a)(a+1)(a+2) is divisble by 24 and 120, and therefore it′s divisble by 8 and 5

Also,(a−2)(a−1)(a) and (a+1)(a+2)(a) are both divisible by 6 and so are both divisible by 3.

Thus(a−2)(a−1)(a)(a+1)(a+2)(a) is divisible by 9.

Therefore,

5⋅8⋅9∣a2(a2−1)(a2−4)

⇒ 360∣a2(a2−1)(a2−4)

We have proved that if a is an arbitrary integer, then 360∣a2(a2−1)(a2−4).

 

Page 25 Problem 20 Answer

We are given,

gcd(a,b) = 1

gcd(a,c) = 1

We have to prove that gcd(a,bc) = 1

We have,

​gcd(a,b) = 1

gcd(a,c) = 1

Therefore,

1 = ax + by

1 = af + ct

for some x,y,f,t in Z

Hence we have,

1 = (ax+by)(af+ct)

= a2xf + abyf + acxt + bcyt

= a(axf+byf+cxt) + bcyt

= ak1+ bck2

Therefore a, bc are relatively prime.

Hence, gcd(a,bc) = 1

We have proved that if,

gcd(a,b) = 1,

and gcd(a,c) = 1,

then gcd(a,bc) = 1

We are given,

gcd(a,b) = 1

c∣a

We have to prove gcd(b,c) = 1

We have gcd(a,b) = 1

Therefore ax + by = 1 for some x,y in Z

Also as c∣a

There exist as in Z such that cs=a, where cs belongs to Z

Therefore,

cst + bf = 1

Thus gcd(b,c) = 1

We have proved that if gcd(a,b) = 1 and c∣a then, gcd(b,c) = 1

We have to prove that if gcd(a,b) = 1 then,

gcd(ac,b) = gcd(c,b)

Let gcd(c,b) = d, then there exists x,y in Z such that,

d = cx + by.

Since d∣c there existsn such that dn = c, and so we have,

d(na) = ca⟹d∣ca

⇒ d∣ca.

Now let k∣ac and k∣b, then there exists m such that km = b, therefore

d = cx + kmy.

Since gcd(a,b) = 1, there exists p,q such that,

ap + bq = 1

Therefore,

apc + bqc = c

⇒ d = (apc+bqc)x + kmy

d = acpx + knqcx + kmy

Butk∣ac

Hence there existsr such that kr = ac

Therefore,

d = krpx + knqcx + kny

d = k(rpx+nqcx+ny)

And hence k∣d and therefore gcd(c,b) = gcd(ac,b)

We have proved that if gcd(a,b) = 1 then,

gcd(ac,b) = gcd(c,b)

We are given,

gcd(a,b) = 1

c∣a+b

We have to prove that,

gcd(a,c) = 1

gcd(b,c) = 1

If gcd(a,b) = c then there exists, x,y in Z such that,

c = ax + by

We have,c∣a + b therefore, there existsn such that cn = a + b and hence,

a = cn−b

Therefore,

(cn−b)x + by = 1

cnx − bx + by = 1

cnx + b(y−x) = 1

So gcd(c,b) = 1

Similarly,

cn − a = b

ax + (cn−a)y = 1

ax + cny − ay = 1

a(x−y) + cny = 1

So,gcd(c,a) = 1.

We have proved that if gcd(a,b) = 1, and c∣a + b then,

​gcd(a,c) = 1

gcd(b,c) = 1

We are given,

gcd(a,b) = 1

d∣ac

d∣bc

We have to prove that d∣c

We have,

gcd(a,b) = 1, then for some x,y in Z

ax + by = 1

Therefore,

c = cax + cby…(1)

Now as d∣ac

Therefore,

ac = dr

c = \(\frac{d r}{a}\)

Also,

d∣bc

⇒ bc = dm

⇒ c = \(\frac{d m}{b}\)

Using above (1) we get,

c = \(\frac{d r}{a} a x+\frac{d m}{b} b y\)

c = drx + dmy

c = d(rx+my)

Therefore d|c

We have proved if gcd(a,b) = 1,d∣ac, and d∣bc, then d∣c.

 

Page 26 Problem 21 Answer

Given : d ∣ n is given. We need to prove 2d−1∣2n−1.

We will do it by using the identity.

It is given that d∣n.

We can also write it as dm = n, here m is some integer.

So we can also write :

2n−1 = 2dm−1

= (2d)m−1

Now we will use the identity :

xk-1 = (x−1)(xk-1+xk-2+⋯+x+1)

Now we have ,

2n−1 = (2d)m−1

= (2d-1)((2d)m-1+(2d)m-2+⋯+(2d)+1)

Hence, 2d−1∣2n−1.

2d – 1|2n-1 by using the identity:

xk-1 = (x-1)(xk-1 + xk-2+…+x+1).

235 – 1 is given.

We will verity that 235-1 is divisible by 31 and 127.

We will do it by using the identity.

We have :

31 = 25−1 and 127=27−1

And we have that 5∣35.

Now using the identity :

xk-1 = (x−1)(xk-1+xk-2+⋯+x+1) we have ,

31 = 25−1∣235−1

And similarly we have 7∣35.

So, again using the identity we get :

127 = 27−1∣235−1

Yes, 235−1 is divided by 31 and 127.

Exercise 2.3 Burton Elementary Number Theory Problem Walkthrough

David Burton Elementary Number Theory Solutions Chapter 2 Divisibility Theory In The Integers Exercise 2.3 Page 26 Problem 22 Answer

Given : Let tndenote the nth triangular number.

We will find for what values of n does tn divide the sum t1+t2+⋯+tn.

We will do it by using the formula above.

We have:

t1 + t2 + …+ tn = \(\frac{n(n+1)(n+2)}{6}\)

tn = \(\frac{n(n+1)}{2}\).

Now, therefore:

\(\frac{t_1+t_2+\cdots+t_n}{t_n}=\frac{\frac{n(n+1)(n+2)}{6}}{\frac{n(n+1)}{2}}\)

= \(\frac{n+2}{3}\)

So, at the \(\frac{n+2}{3}\) integer tn divides t1 + t2 + …. + tn.

Therefore, the form of n is n = 3k + 1 and the values of n are 1,4,7,10,……

At the \(\frac{n+2}{3}\) integer tn divides t1 + t2 + …. + tn.

Therefore, the form of n is n = 3k + 1 and the values of n are 1,4,7,10,….

 

Page 26 Problem 23 Answer

a | b is given.

We need to show that a| gcd(a,b)gcd(a,c).

We will prove it by using the formula of gcd(a,b).

a|bc is given that means bc = ax where x∈Z (let us consider this equation one).

Now we have :

gcd(a,b) = am + bn ,where m,n∈Z and

gcd(a,c) = ar + bs , where r,s∈Z.

Now we have :

gcd(a,b)⋅gcd(a,c) = a2mr + acms + abrn + bcns

Now using equation one we get :

= a2mr + acms + abrn + axns

= a(amr+cms+brn+xns)

Hence , a ∣ gcd(a,b)⋅gcd(a,c) is proved.

Yes, a∣gcd(a,b)⋅gcd(a,c) is proved.

David Burton Elementary Number Theory Solutions Chapter 2 Divisibility Theory In The Integers Exercise 2.2

David Burton Elementary Number Theory Solutions Chapter 2 Divisibility Theory In The Integers

Page 19 Problem 1 Answer

Here, we have to prove that if a and b are integers, with b > 0 then there exist unique integers q and r satisfying a = qb + r, where 2b ≤ r < 3b

Proof : By division algorithm, ∃ unique q′ and r′, such that a = q′b + r′,0 ≤ r′ < b

∴ a = q′b + r′ + 2b − 2b = (q′−2)b + r′+2b. Let q = q′− 2,r = r′ + 2b,

Therefore r and q are unique.

Since, 0 ≤ r′ < b, then 2b ≤ r′ + 2b < b + 2b ⟹ 2b ≤ r < 3b

Thus, we have proved that if a and b are integers, with b > 0,then there exist unique integers q and r satisfying a = qb + r, where 2b ≤ r < 3b

David Burton Elementary Number Theory Chapter 2 Exercise 2.2 Solutions

Page 19 Problem 2 Answer

Here, we have to show that any integer of the form 6k + 5 is also of the form 3j + 2,but not conversely

Proof : If a = 6k + 5 = 3⋅2k + 3 + 2 = 3(2k+1)+ 2 = 3j+ 2 where j = 2k + 1. To disprove that any integer of the form 3j + 2 is also of the form 6k + 5.Take 3j + 2 where j is even, i.e j = 2r ⇒ 3(2r) + 2 = 6r + 2,but r and 2 are unique, so 3j + 2 ≠ 6k + 5

Thus, we proved that any integer of the form 6k + 5 is also of the form 3j + 2, but not conversely

 

Page 19 Problem 3 Answer

Here, we have to use the Division Algorithm to establish, the square of any integer is either of the form 3k or 3k + 1

Proof : By division algorithm ∃a and q such that a = 3q,a = 3q + 1 or a = 3q + 2

If a = 3q: ∴ a2 = 9q2 = 3(3q2) = 3k where k = 3q2

If a = 3q + 1: ∴ a2 = 9q2 + 6q + 1 = 3(3q2+2q) + 1 = 3k + 1 where k = 3q2 + 2q

If a = 3q + 2: ∴ a2 = 9q2 + 12q + 4 = 9q2 + 12q + 3 + 1 = 3(3q2+4q+1) + 1 = 3k+1 where k = 3q2 + 4q + 1

David Burton Elementary Number Theory Solutions Chapter 2 Divisibility Theory In The Integers Exercise 2.2

Thus, we use the Division Algorithm to establish, the square of any integer is either of the form 3k or 3k+1

Here, we have to use the Division Algorithm to establish, the cube of any integer has one of the forms: 9k, 9k+1 or 9k+8

Proof : By division algorithm ∃a and q such that a = 3q+r,r = 0,1,2

If \(a=3 q: (3 q)^3=27 q^3=9\left(3 q^3\right)=9 k \text { where } k=3 q^3\)

If \(a = 3 q+1: (3 q+1)^3=\left(\begin{array}{l}
3 \\
0
\end{array}\right)(3 q)^3+\left(\begin{array}{l}
3 \\
1
\end{array}\right)(3 q)^2+\left(\begin{array}{l}
3 \\
2
\end{array}\right) 3 q+\left(\begin{array}{l}
3 \\
3
\end{array}\right)\)

=\(27 q^3+27 q^2+9 q+1\)

=\(9\left(3 q^3+\right.\left.3 q^2+q\right)+1\)

=\(9 k+1 \text { where } k=3 q^3+3 q^2+q\)

If a = \(3 q+2: (3 q+2)^3=\left(\begin{array}{l}
3 \\
0
\end{array}\right)(3 q)^3+\left(\begin{array}{c}
3 \\
1
\end{array}\right)(3 q)^2 \cdot 2+\left(\begin{array}{l}
3 \\
2
\end{array}\right) 3 q \cdot 2^2+\left(\begin{array}{c}
3 \\
3
\end{array}\right) \cdot 2^3\)

=\(27 q^3+54 q^2+36 q+8\)

= \(9\left(3 q^3+3 q^2+4 q\right)+8=9 k+8 \text { where } k=3 q^3+3 q^2+4 q\)

Thus, we used the Division Algorithm to establish, the cube of any integer has one of the forms : 9k, 9k+1 or 9k+8

Here, we have to use the Division Algorithm to establish the fourth power of any integer is either of the form : 5k, 5k+1

Proof : By division algorithm, ∃a and q such that a = 5q + r,0 ≤ r < 5.Consider n4 = (5q+r)4,from binomial expansion, each term is a factor of 5 except last term.

\((5 q+r)^4=\left(\begin{array}{c}
4 \\
0
\end{array}\right)(5 q)^4+\left(\begin{array}{c}
4 \\
1
\end{array}\right)(5 q)^3 r+\left(\begin{array}{c}
4 \\
2
\end{array}\right)(5 q)^2 r^2+\left(\begin{array}{c}
4 \\
1
\end{array}\right)(5 q) r^3+r^4\)

⇒ \((5 q+r)^4=5\left[\left(\begin{array}{c}
4 \\
0
\end{array}\right) 5^3 q^4+\left(\begin{array}{c}
4 \\
1
\end{array}\right) 5^2 q^3 r+\left(\begin{array}{c}
4 \\
2
\end{array}\right) 5 q^2 r^2+\left(\begin{array}{c}
4 \\
1
\end{array}\right) q r^3\right]+r^4\)

⇒ \((5 q+r)^4=5 k+r^4 \text { where } k=\left(\begin{array}{c}
4 \\
0
\end{array}\right) 5^3 q^4+\left(\begin{array}{c}
4 \\
1
\end{array}\right) 5^2 q^3 r+\left(\begin{array}{c}
4 \\
2
\end{array}\right) 5 q^2 r^2+\left(\begin{array}{c}
4 \\
1
\end{array}\right) q r^3\)

If r = 0 then r4 = 0, and n4 = 5k as all other terms have 5 as a factor

If r = 1 then r4 = 1,then clearly n4 = 5k + 1

If r = 2 then r4 = 16 = 15 + 1 = 3⋅5 + 1, so n4 = 5k + 1

If r = 3 then r4 = 81 = 80 + 1 = 5⋅16 + 1, so n4 = 5k + 1

If r = 4 then r4 = 256 = 255 + 1 = 5⋅51 + 1, so n4 = 5k + 1

Thus, we use the Division Algorithm to establish the fourth power of any integer is either of the form 5k or 5k+1

Solutions To Chapter 2 Exercise 2.2 Burton Number Theory

David Burton Elementary Number Theory Solutions Chapter 2 Divisibility Theory In The Integers Exercise 2.2 Page 19 Problem 4 Answer

Here, we have to prove that 3a2 − 1 is never a perfect square

Proof :

Suppose 3a2 − 1 = n2, some n by Ex3(a),

3a2 − 1 = 3k + 1 or 3a{2} − 1 = 3k

∴ 3(a2−k) = 2 or 3(a2−k) = 1,

but each are impossible, since by division algorithm, 2 = 3⋅0 + 2 and 1 = 3⋅0 + 1

Thus, we proved that 3a2 − 1 is never a perfect square.

 

Page 19 Problem 5 Answer

Here, we have to prove that n(n+1)(2n+1)/6 is an integer.

Proof: By division algorithm, ∃n and k such that n = 6k + r, 0 ≤ r < 6. Let A = \(\frac{n(n+1)(2 n+1)}{6}\)

If r = 0 then, A = k(6k+1)(12k+1) is an integer

If r = 1 then

A = \(\frac{(6 k+1)(6 k+2)(12 k+3)}{6}\)

A = \(\frac{(6 k+1) 2(3 k+1) 3(4 k+1)}{6}\)

= (6k+1)(3k+1)(4k+1) is an integer

If r = 2 then

A = \(\frac{(6 k+2)(6 k+3)(12 k+5)}{6}\)

A = \(\frac{2(3 k+1) 3(2 k+1) (12 k+5)}{6}\)

= (6k+1)(3k+1)(4k+1) is an integer

If r = 3 then,

A = \(\frac{(6 k+3)(6 k+4)(12 k+7)}{6}\)

A = \(\frac{3(2 k+1) 2(3 k+1) (12 k+7)}{6}\)

= (2k+1)(3k+2)(12k+7) is an integer

If r = 4 then

A = \(\frac{(6 k+4)(6 k+5)(12 k+9)}{6}\)

A = \(\frac{2(3 k+2) (6 k+5) 3(4 k+3)}{6}\)

= (3k+2)(6k+5)(4k+3) is an integer

If r = 5 then,

A = \(\frac{(6 k+5)(6 k+6)(12 k+11)}{6}\)

A = \(\frac{(6 k+5) 6( k+1) (12 k+11)}{6}\)

= (6k+1)(3k+1)(4k+1) is an integer

Thus for n ≥ 1, \(\frac{n(n+1)(2 n+1)}{6}\) is an integer.

Thus, we prove that for n ≥ 1 n(n+1)(2n+1)/6 is an integer

 

Page 19 Problem 6 Answer

Here, we have to show that the cube of any integer is of the form 7k or 7k ± 1

Proof : By division algorithm, ∃n and q such that n = 7q + r,0 ≤ r < 7.Consider n3 = (7q+r)3,from binomial expansion, each term is a factor of 7 except last term,

(7q+r)3 = \(\left(\begin{array}{l}
3 \\
0
\end{array}\right)(7 q)^3+\left(\begin{array}{l}
3 \\
1
\end{array}\right)(7 q)^2 r+\left(\begin{array}{l}
3 \\
2
\end{array}\right)(7 q)^2 r^2+r^3\)

If r = 0 then, r3 = 0and n3 = 7k as all other terms have 7 as a factor.

If r = 1then, r3 = 1,then clearly n3 = 7k + 1

If r = 2then,

r3 = 8 = 7 + 1, so n3 = 7k + 1

If r = 3then,

r3 = 27 = 28 − 1 = 4⋅7 − 1, sо n3 = 7k − 1

If r = 4then,

r3 = 64 = 63 + 1 = 9⋅7 + 1, and n3 = 7k + 1

If r = 5then,

r3 = 125 = 126−1 = 18⋅7 − 1, so n3 = 7k − 1

If r = 6then,

r3 = 216 = 217 − 1 = 31⋅7 − 1, so n3 = 7k + 1

Thus, the cube of any integer is of the form 7k, 7k+1 or 7k−1

Divisibility Theory Exercise 2.2 Answers David Burton

David Burton Elementary Number Theory Solutions Chapter 2 Divisibility Theory In The Integers Exercise 2.2 Page 19 Problem 7 Answer

Obtain the following version of the Division Algorithm: For integers a and b, with b ≠ 0, there exist unique integers q and r that satisfy a = qb + r, where \(-\frac{1}{2}|b|<r \leq \frac{1}{2}|b|\).

It is required to obtain a following version of Division Algorithm: For integers a and b, with b≠0, there exists unique integers q and r that satisfy a = qb + r, where \(-\frac{1}{2}|b|<r \leq \frac{1}{2}|b|\).

The division algorithm for integers states that given any two integers a and b with b > 0, there exists unlque integers q and r such that a = qb + r, where 0 ≤ r < b.

Therefore, according to the division algorithm, there exists unique integers q′ and r′ such that a = q′b + r′, where 0 ≤ r′ < ∣b∣. Consider 0 < ∣b∣, this can be further divided into intervals, 0 < \(\frac{1}{2}|b|\) and \(\frac{1}{2}|b|\) < ∣b∣

Now, if 0 ≤ r’ ≤ \(\frac{1}{2}|b|\), let r = r’ and q = q’, and if \(\frac{1}{2}|b|\) < r’ < |b|, then \(-\frac{1}{2}|b|\) < r’ – |b| < 0, this gives,

a = q’b + r’ – |b| + |b|

If |b| ≥ 0, then |b| = b, that is,

a = q’b + r’ – |b| + b

This gives,

a = (q′+1)b + r′ − ∣b∣, therefore, let q = q′ + 1 and r = r′ − ∣b∣

If ∣b∣ < 0, then ∣b∣ = −b, that is,

a = q′b + r′ − ∣b∣ − b

This gives, a = (q′−1)b + r′ − ∣b∣, therefore, let q = q′ − 1 and r = r′ − ∣b∣

Therefore, if

\(\frac{1}{2}|b|\) < r’ < |b| = |b| – \(\frac{1}{2}|b|\) < r’ < |b| ⇒ \(-\frac{1}{2}|b|\) < r’ < 0 ⇒ \(-\frac{1}{2}|b|\) < r’ < 0 < \(\frac{1}{2}|b|\),

that is,

\(-\frac{1}{2}|b|<r^*<\frac{1}{2}|b|, \text { letr }=r^{\prime}-|b| a n d q=q^{\prime}+\frac{|b|}{b}\)

Hence, for integers a and b. with b ≠ 0, there exists unique integers q and r that satisfy a = qb + r, where \(-\frac{1}{2}|b|<r \leq \frac{1}{2}|b|\).

 

Page 19 Problem 8 Answer

Here, we have to prove that no integer in the following sequence is a perfect square: 11,111,1111,11111,…

It’s given that a typical term 111⋅⋅⋅⋅⋅111 can be written as

111⋯111 = 111⋯108 + 3 = 4k + 3

Proof: Any number in sequence can be written as

A = 11 + 100 + 1000 + ….. = 11 + \(\sum_{i=2}^n 10^i\)

Each term of \(\sum_{i=2}^n 10^i\) is divisible by 4. So,

Ai= 11 + 4ri = 4(r+2) + 3, for certain ri

So, Ai = rr’i + 3 by division algorithm, r’ and 3 are unique. Suppose Ai = s2 let s = 4q + r

r ≠ 0,as

s2 = 16q2 = 4(4q2),which is not of the form 4ri′ + 3

r ≠ 1,as

s2 = 16q2 + 8q + 1 = 4(4q2+2q) + 1,which is not of the form 4ri′ + 3

r ≠ 2,as

s2 = 16q2 + 16q + 4 = 4(4q2 + 4q + 1),which is not of the form 4ri′ + 3

r ≠ 3,as

s2 = 16q2 + 24q + 9 = 4(4q2 + 2q + 2) + 1,which is not of the form 4ri′ + 3

Therefore there is no s such that s2 = 4ri + 3. All Ai are not perfect squares

Thus, we proved that no integer in the following sequence is a perfect square, 11,111,1111,11111,…

 

David Burton Elementary Number Theory Solutions Chapter 2 Divisibility Theory In The Integers Exercise 2.2 Page 19 Problem 9 Answer

Here, we have to verify that if an integer is simultaneously a square and a cube (as is the case with 64 = 82 = 43),then it must be either of the form 7k or 7k+1

Proof : By division algorithm, ∃s and k such that s = 7k + b,0 ≤ b < 7.Consider s3 = (7k+b)3, from binomial expansion, each term is a factor of 7 except last term,

(7k+b)3 = \(\left(\begin{array}{c}
3 \\
0
\end{array}\right)(7 k)^3+\left(\begin{array}{c}
3 \\
1
\end{array}\right)(7 k)^3 b+\left(\begin{array}{c}
3 \\
2
\end{array}\right)(7 k)^2 b^2+b^3\)

If b = 0 then, b3 = 0, and n3 = 7k as all other terms have 7 as a factor.

If b = 1 then, b3 = 1,then clearly n3 = 7k + 1

If b = 2 then,

b3 = 8 = 7 + 1,so n3 = 7k + 1

If b = 3 then,

b3 = 27 = 28 − 1 = 4⋅7 − 1, so n3 = 7k − 1

If b = 4 then,

b3 = 64 = 63 + 1 = 9⋅7 + 1, and n3 = 7k + 1

If b = 5 then,

b3 = 125 = 126 − 1 = 18⋅7 − 1, so n3 = 7k − 1

If b = 6 then,

b3 = 216 = 217 − 1 = 31⋅7−1, so n3 = 7k + 1

Now by division algorithm, ∃r and c such that r = 7c + d,0 ≤ d < 7 then,

If d = 0 then,r2 = 7(7c2) = 7k

If d = 1 then,

r2 = 49c2 + 14c + 1 = 7(7c2+2c) + 1 = 7k + 1

If d = 2 then,

r2 = 49c2 + 28c + 4 = 7(7c2+4c) + 4 = 7k + 4

If d = 3 then,

r2 = 49c2 + 42c + 9 = 7(7c2+6c+1) + 2 = 7k + 2

If d = 4 then,

r2 = 49c2 + 56c + 16 = 7(7c2+8c+2) + 2 = 7k + 2

If d = 5 then,

r2 = 49c2 + 70c + 25 = 7(7c2+10c+3) + 4 = 7k + 4

If d = 6 then,

r2 = 49c2 + 84c + 36 = 7(7c2+12c+5) + 1 = 7k + 1

Thus r2 is of the form : 7k, 7k+1, 7k+2 or 7k+4 and s3 is of the form :7k, 7k+1 or 7k+6. By uniqueness part of division algorithm, A must be either of form 7k or 7k+1

Thus, we verify that if an integer is simultaneously a square and a cube (as is the case with 64 = 82 = 43),then it must be either of the form 7k or 7k+1

How To Solve Chapter 2 Exercise 2.2 Burton Number Theory

Page 19 Problem 10 Answer

Here, we have to establish that the integer n(7n2+5) is of the form 6k

By division algorithm n=6k+r, 0 ≤ r < 6

If n = 6k then,(6k)(7(36k2)+5) = 6t

If n = 6k + 1 then,

(6k+1)(7(6k+1)2+5) = (6k+1)(7(36k2+12k+1)+5) = 6(6k+ 1) (7(6k2+2k)+2) = 6t

If n = 6k + 2 then,

2(3k+1)(7(6k+2)2+5) = 2(3k+1)(7(36k2+24k+4)+5) = 6(3k+ 1) (7(12k2+8k)+11) = 6t

If n = 6k + 3 then,

3(2k+1)(7(6k+3)2+5) = 3(2k+1)(7(36k2+36k+9)+5) = 6(6k+ 1) (7(18k2+18k)+34) = 6t

If n = 6k + 4then,

2(3k+2)(7(6k+4)2+5) = 2(3k+2)(7(36k2+48k+16)+5) = 2(3k+ 2) (7(12k2+16k)+39) = 6t

If n = 6k + 5 then,

(6k+5)(7(6k+5)2+5) = (6k+5)(7(36k2+60k+25)+5) = (6k+5)(7(36k2+60k)+180) = 6(6k+5)(7(6k2+10k)+30) = 6t

Thus, in all cases we have n(7n2+5) is of the form 6k

Thus, we establish that the integer n(7n2+5) is of the form 6k

Elementary Number Theory Burton Chapter 2 Exercise 2.2 Explanations

David Burton Elementary Number Theory Solutions Chapter 2 Divisibility Theory In The Integers Exercise 2.2 Page 19 Problem 11 Answer

Here, we have to show that n4 + 4n2 + 11 is of the form 16k

Since, n is odd then n = 2r + 1

n4 + 4n2 + 11 = (n2+2)2 + 7

= [(2r+1)2+2]2 + 7

= (4r2+4r+1+2)2 + 7

= (4r2+4r+3)2 + 7

= [(4r2+4r)+3]2 + 7

= (4r2+4r)2 + 2⋅(4r2+4r)⋅3 + 9 + 7

= 16r4 + 2⋅4r2⋅4r + 16r2 + 24r2 + 24r + 9 + 7

= 16r4 + 32r3 + 16r2 + 24r2 + 24r + 9 + 7

= 16r4 + 32r3 + 40r2 + 24r + 16

Now, by division algorithm, r = 2q or 2q + 1

If r = 2q: ​

​16(2q)4 + 32(2q)3 + 40(2q)2 + 24(2q) + 16

= 16[(2q)4 + 2(2q)3 + 10q2 + 3q + 1]

= 16k

If r = 2q + 1:​

​16(2q+1)4 + 32(2q+1)3 + 40(2q+1)2 + 24(2q+1) + 16

= 16(2q+1)4 + 32(2q+1)3 + 160q2 + 160q + 40 + 48q + 24 + 16

= 16[(2q+1)4 + 2(2q+1)3 + 10q2 + 10q + 3q + 4 + 1]

= 16k

Thus, we showed that n4 + 4n2 + 11 is of the form 16k