Question

maths class 9 number system formulas​

Answer 1

Answer:

Step-by-step explanation:

Natural Numbers N = {1,2,3,4,5..........}

It is the counting numbers

2 Whole number W= {0,1,2,3,4,5........}

It is the counting numbers + zero

3 Integers Z={...-7,-6,-5,-4,-3,-2,-1,0,1,2,3,4,5,6...}

4 Positive integers Z+= {1,2,3,4,5........}

5 Negative integers Z-={...-7,-6,-5,-4,-3,-2,-1}

6 Rational Number A number is called rational if it can be expressed

in the form p/q where p and q are integers ( q>

0).

Example : 1⁄2 , 4/3 ,5/7 ,1 etc.

7 Irrational Number A number is called rational if it cannot be

expressed in the form p/q where p and q are

integers ( q> 0).

Example : etc

8. Real Numbers: All rational and all irrational number makes the

collection of real number. It is denoted by the

letter R

9 What is zero Zero number definition

Zero is a number used in mathematics to

describe no quantity or null quantity.It is also

used as placeholder digit in many numbers

The modern 0 symbol was invented in India in

the 6-th century, used later by the Persians and

Class 9

Important Formulas

Chapter 1 - Number System

Arabs and later in Europe.

Important facts about zero

1) Zero is a number but it is neither positive nor

negative number.

So it is not included in the set of positive number

nor negative numbers.

But it is included in the set of non-negative

numbers

2) Zero is an even number

3) Zero is not a prime nor a composite number.

It cannot be prime because it has an infinite

number of factors and cannot be composite

because it cannot be expressed by multiplying

prime numbers (0 must always be one of the

factors)