1. Chapter One Basic Concepts
Afjal Hossain
Assistant Professor
Department of Marketing, PSTU

2. Definition of the Term Definition Example Natural Number:
All the positive whole numbers are called natural numbers. The smallest natural number is 1 but there is no largest natural number. Properties:
a. Natural number + Natural number = Natural number
b. Natural number x Natural number = Natural number
Ex1, 25, 1025 etc.
Integer
An integer consists of positive numbers, zero and negative numbers. Integers are of 2 types: Even & Odd.
-5, 0, 25 etc.

3. Definition of the Term Definition Example Even Integer
An integer is an even integer which is divided by 2. Properties:
a. Even number + Even number = Even number
b. Even number x Even number = Even number
2, 28, 2n etc.
Odd Integer
An integer is an odd integer which is not divided by 2. Properties:
a. Odd number + Odd number = Even number
b. Odd number x Odd number = Odd number
5, 27, (2n+1) etc.

4. Definition of the Term Definition Example Rational Number
The number which has a numerator and a denominator is rational number. In other words, A rational number is a number which can be put in the form p/q, where p & q are integers and q is not equal to zero. Here p and q are termed as numerator and denominator.
5/8, 3/2 etc.
Irrational Number
When a number cannot be expressed as p/q but p and q are integers and q ≠ 0, then it is called irrational number.
√2, √3, √31 etc.

5. Definition of the Term Definition Example Real Number
The collection of all the rational and irrational numbers is called the system of real numbers.
5/8, √3 etc.
Prime Number
A number which is not exactly divisible by any number except itself and unity is called a prime number or a prime.
1, 3, 5, 7, 11,13 etc.

6. Definition of the Term Definition Example Composite Number
A number which is divisible by other numbers besides itself and unity is called a composite number.
35, 56 etc.
Absolute value of a number
The absolute value denoted by │a│ of a real number a. The absolute value of a number is always positive. Properties:
a) If ‘a’ is positive or zero, then │a│= a
b) If ‘a’ is negative, then │-a│= a
c) Symbolically we can write a ≥ 0 and a < 0
│5│=5, │-10│=10 etc.

7. Properties of zero o/a, where a = 0 a/o, where a ≠ 0
o/o is not determinate

8. Inequality of Numbers
If a and b are two numbers, then we can say that:
a) a < b when a is less than b or (b-a) condition
b) a > b when a is greater than b or (a-b) condition
c) a ≥ b when a is greater than or equal to b
d) a ≤ b when a is less than or equal to b