PROPERTIES OF MULTIPLICATION OF INTEGERS

In Math, the whole numbers and negative numbers together are called integers. The set of all integers is denoted by Z.

Z  =  {... - 2, - 1,0,1,2, ...}, is the set of all integers

Here, we are going to see the following three properties of multiplication of integers. 

(i)  Closure property

(ii)  Commutative property

(iii)  Associative property

(iv)  Multiplicative identity

Closure Property of Multiplication of Integers

Observe the following:

– 10 × (– 5) = 50

40 × (– 15) = – 600

In general, a × b is an integer, for all integers a and b.

Therefore, integers are closed under multiplication.

Commutative Property of Multiplication of Integers

Observe the following :

5 × (– 6) = – 30 and (– 6) × 5 = – 30

Therefore,

5 × (– 6) = (– 6) × 5

In general, for any two integers a and b,

a × b = b × a

Therefore, multiplication is commutative for integers.

Associative Property of Multiplication of Integers

Consider the integers 2, – 5, 6.

Look at

[2 x (-5)] x 6  =  -10 x 6  =  -60

2 x [(- 5) x 6]  =  2 x (-30)  =  -60

Thus,

[2 x (-5)] x 6  =  2 x [(- 5) x 6]

In general, for any integers a, b, c,

(a × b) × c  =  a × (b × c)

So, we can say that integers are associative under multiplication.

Multiplication by Zero

The product of any nonzero integer with zero is zero.

Observe the following:

5 × 0 = 0

– 8 × 0 = 0

In general, for any nonzero integer a

a × 0 = 0 × a = 0

Multiplicative Identity

Observe the following:

5 x 1  =  5

1 x (- 7)  =  -7

This shows that ‘1’ is the multiplicative identity for integers.

In general, for any integer a we have

a x 1  =  1 x a  =  a

Distributive Property of Multiplication of Integers

Multiplication is Distributive Over Addition :

Consider the integers 12, 9, 7.

Look at

12 x (9 + 7)  =  12 x 16  =  192

12 x (9 + 7)  =  12 x 9  +  12 x 7  =  108 + 84  =  192

Thus 12 x (9 + 7)  =  (12 x 9) + (12 x 7)

In general, for any integers a, b, c.

a x (b + c)  =  (a x b) + (a x c)

Therefore, multiplication is distributive over addition of integers.

Multiplication is Distributive Over Subtraction :

Consider the integers 12, 9, 7.

Look at

12 x (9 - 7)  =  12 x 2  =  24

12 x (9 - 7)  =  12 x 9  -  12 x 7  =  108 - 84  =  24

Thus 12 x (9 - 7)  =  (12 x 9) - (12 x 7)

In general, for any integers a, b, c.

a x (b - c)  =  (a x b) - (a x c)

Therefore, multiplication is distributive over subtraction of integers.

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