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

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.

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.

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.

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.

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.

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

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