## Pre – Requisites

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**Speed Notes**

**Notes For Quick Coverage**

**Introduction to Natural Numbers**

Non-negative counting numbers excluding zero are called **Natural Numbers**.

N = 1, 2, 3, 4, 5, ……….

**Whole Numbers**

All natural numbers including zero are called **Whole Numbers**.

W = 0, 1, 2, 3, 4, 5, ……………. **(Scroll down to continue …)**

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**Integers**

All natural numbers, negative numbers and 0, together are called **Integers**.

Z = – 3, – 2, – 1, 0, 1, 2, 3, 4, …………..

**Rational Numbers**

The number ‘a’ is called **Rational** if it can be written in the form of r/s where ‘r’ and ‘s’ are integers and s ≠ 0,

Q = 2/3, 3/5, etc. all are rational numbers.

**How to find a rational number between two given numbers?**

To find the rational number between two given numbers ‘a’ and ‘b’.

**Example:**

Find 2 rational numbers between 4 and 5.

**Solution:**

To find the rational number between 4 and 5

To find another number we will follow the same process again.

Hence the two rational numbers between 4 and 5 are 9/2 and 17/4.

**Remark: **There could be unlimited rational numbers between any two rational numbers.

**Irrational Numbers**

The number ‘a’ which can’t be written in the form of p/q is called irrational. Here, p and q are integers and q ≠ 0. You can say that the numbers which are not rational are called **Irrational Numbers**.

**Example –** √7, √11 etc.

**Real Numbers**

All numbers including both rational and irrational numbers are called **Real Numbers**.

R = – 2, – (2/3), 0, 3 and √2

**Real Numbers And Their Decimal Expansions**

**1. Rational Numbers**

If the rational number is in the form of a/b, then we can get two situations by dividing a by b.

**a. If the remainder becomes zero**

While dividing if we get zero as the remainder after some steps then the decimal expansion of such a number is called terminating.

**Example:**

7/8 = 0.875

**b. If the remainder does not become zero**

While dividing if the decimal expansion continues and not becomes zero then it is called non-terminating or repeating expansion.

**Example:**

1/3 = 0.3333….

Hence, the decimal expansion of rational numbers could be terminating or non-terminating recurring and vice-versa.

**2. Irrational Numbers**

If we do the decimal expansion of an irrational number then it would be **non –terminating non-recurring **and vice-versa. i. e. the remainder does not become zero and also not repeated.

**Example:**

π = 3.141592653589793238……

**Representing Real Numbers on the Number Line**

To represent the real numbers on the number line, we use the process of successive magnification. We visualise the numbers through a magnifying glass on the number line.

**Example:**

**Step 1:** The number lies between 4 and 5, so we divide it into 10 equal parts. Now for the first decimal place, we will mark the number between 4.2 and 4.3.

**Step 2:** Now we will divide it into 10 equal parts again. The second decimal place will be between 4.26 and 4.27.

**Step 3:** Now we will again divide it into 10 equal parts. The third decimal place will be between 4.262 and 4.263.

**Step 4:** By doing the same process again we will mark the point at 4.2626.

**Operations on Real Numbers**

1. The sum, difference, product and quotient of two rational numbers will be rational.

**Example:**

2. If we add or subtract a rational number with an irrational number then the outcome will be irrational.

**Example:**

If 5 is a rational number. √7 is an irrational number. Then, 5 + √7 and 5 – √7 are irrational numbers.

3. If we multiply a non-zero rational number with an irrational number, the outcome will be irrational. If we divide a non-zero rational number with an irrational number, the outcome will also be irrational.

**Example:**

If 7 is a rational number and √5 is an irrational number then 7√7 and 7/√5 are irrational numbers.

4. The sum, difference, product and quotient of two irrational numbers could be rational or irrational.

**Example:**

**Finding Roots of a Positive Real Number ‘x’ geometrically and mark it on the Number Line**

To find √x geometrically

1. First, mark the distance x unit from point A on the line. This ensures that AB equals x unit.

2. From B mark a point C with the distance of 1 unit, so that BC = 1 unit.

3. Take the midpoint of AC and mark it as O. Then take OC as the radius and draw a semicircle.

4. From the point B draw a perpendicular BD which intersects the semicircle at point D.

**The length of BD** **= √x.**

To mark the position of √x on the number line, we will take AC as the number line. B will be zero. So C is point 1 on the number line.

Now we will take B as the centre and BD as the radius. We will draw the arc on the number line at point E.

Now E is √x on the number line.

**Identities Related to Square Roots**

If p and q are two positive real numbers

**Examples:**

1. Simplify

We will use the identity

2. Simplify

We will use the identity

**Rationalising the Denominator**

Rationalising the denominator means to convert the denominator containing a square root term into a rational number. This is done by finding the equivalent fraction of the given fraction.

For which we can use the identities of the real numbers.

**Example:**

Rationalise the denominator of 7/(7- √3).

**Solution:**

We will use the identityhere.

**Laws of Exponents for Real Numbers**

If we have a and b as the base and m and n as the exponents, then

1. a^{m} × a^{n} =a^{m+n}

^{ }2. (a^{m})^{n} = a^{mn}

4. a^{m }b^{m} = (ab)^{m}

5.^{ }a^{0} = 1

6. a^{1} = a

7. 1/a^{n} = a^{-n}

- Let a > 0 be a real number and n a positive integer.

- Let a > 0 be a real number. Let m and n be integers. They have no common factors other than 1. Also, n > 0. Then,

**Example:**

Simplify the expression (2x^{3}y^{4}) (3xy^{5})^{2}.

**Solution:**

Here we will use the law of exponents

a^{m} × a^{n} =a^{m+n} and (a^{m})^{n} = a^{mn}

(2x^{3}y^{4})(3xy^{5})^{2}

(2x^{3}y^{4})(3 ^{2} x ^{2} y^{10})

18. x^{3}. x^{2}. y^{4}. y^{10}

18. x^{3+2}. y^{4+10}

18x^{5}y^{14}

Here’s a simple outline for an eBook on Real Numbers:

Title: Understanding Real Numbers: A Comprehensive Guide

Table of Contents

- Introduction to Real Numbers

What are Numbers?

Introduction to Real Numbers

Why Are Real Numbers Important?

- Classification of Numbers

Natural Numbers

Whole Numbers

Integers

Rational Numbers

Irrational Numbers

- Properties of Real Numbers

Closure Property

Commutative Property

Associative Property

Distributive Property

Identity and Inverse Elements

- The Real Number Line

Concept of Number Line

Plotting Real Numbers on the Number Line

Understanding Density of Real Numbers

- Rational and Irrational Numbers

Definition of Rational Numbers

Properties of Rational Numbers

Definition of Irrational Numbers

Examples of Irrational Numbers (like √2, π, e)

Proving √2 is Irrational

- Decimals and Real Numbers

Finite and Infinite Decimals

Terminating and Non-Terminating Decimals

Relationship between Decimals and Fractions

- Operations on Real Numbers

Addition and Subtraction

Multiplication and Division

Operations with Decimals

Operations with Irrational Numbers

- Absolute Value and Real Numbers

Definition of Absolute Value

Geometric Representation on the Number Line

Properties of Absolute Value

- The Concept of Infinity

Understanding Infinite Sets

Limits and Real Numbers

Approaching Infinity on the Number Line

- Applications of Real Numbers

In Geometry (Pythagorean Theorem)

In Calculus (Limits, Derivatives, and Integrals)

In Daily Life (Measurements, Finance, etc.)

- Advanced Topics on Real Numbers

Real Numbers in Algebra

Real Numbers and Functions

Real Numbers and Continuity

- Conclusion

Summary of Key Concepts

Importance of Mastering Real Numbers

How Real Numbers Apply to Higher Mathematics

Chapter 1: Introduction to Real Numbers

What Are Numbers?

Numbers are abstract symbols used to represent quantities. Throughout history, different types of numbers have been developed to address various mathematical problems.

Introduction to Real Numbers

Real numbers are all the numbers that can be found on the number line. This includes rational numbers (such as 5, -3, and 0.75) and irrational numbers (such as √2 and π). Together, they form the building blocks of modern mathematics.

Real numbers are used to measure continuous quantities like distance, time, and weight. They are integral to the concepts of calculus, physics, engineering, and many other fields.

Why Are Real Numbers Important?

Real numbers play a critical role in mathematics. They allow us to describe the size of objects, calculate areas and volumes, and express very large or very small values. Without real numbers, much of modern science and technology would not exist.

Chapter 2: Classification of Numbers

Natural Numbers

The set of natural numbers consists of counting numbers, such as 1, 2, 3, and so on. These are the simplest type of numbers and do not include zero.

Whole Numbers

Whole numbers are like natural numbers but also include zero. Thus, the set is {0, 1, 2, 3,…}.

Integers

Integers expand on whole numbers by including negative numbers. The set of integers is {…, -3, -2, -1, 0, 1, 2, 3,…}.

Rational Numbers

Rational numbers are numbers that can be expressed as a fraction of two integers (a/b), where b ≠ 0. Examples of rational numbers include 1/2, -4, and 0.75.

Irrational Numbers

Irrational numbers cannot be expressed as a fraction of two integers. Examples include √2, π, and e. These numbers have non-repeating, non-terminating decimal expansions.

Chapter 3: Properties of Real Numbers

Closure Property

The set of real numbers is closed under addition, subtraction, multiplication, and division (except division by zero). This means that the result of any of these operations on two real numbers will always yield another real number.

Commutative Property

For any two real numbers a and b:

Addition: a + b = b + a

Multiplication: a × b = b × a

Associative Property

For any three real numbers a, b, and c:

Addition: (a + b) + c = a + (b + c)

Multiplication: (a × b) × c = a × (b × c)

Distributive Property

The distributive property connects addition and multiplication:

a × (b + c) = (a × b) + (a × c)

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