# CLASS-7INFINITE SET

INFINITE SET

Infinite Set, if the members of the Set is countless

It is not easy to write infinite sets in the tabular form because it is not possible to make a list of an infinite number of members. We do write the special sets like, A, B, C, D, E, F, G in the tabular form as given below -

For Example–

1) The Set ‘A’ of whole numbers, i.e. A = { 0, 1, 2, 3, 4, ………}

2) The Set ‘B’ of natural numbers, i.e. B = { 1, 2, 3, 4, 5, ……….}

3) The Set ‘C’ of odd natural numbers, i.e. = { x/x is an odd natural numbers } = {…….,-5, -4, -3, -2, -1, 0, 1, 2, 3, 4, 5,………}

4) The Sets ‘D’ of odd positive numbers, i.e. = { 1, 3, 5, 7,………….}

5) The Sets ‘E’ of odd negative numbers, i.e. = {…….,-5, -4, -3, -2, -1, 0,…...}

6) The Sets ‘F’ of even positive numbers, i.e. = { 2, 4, 6, 8, 10, 12, ………..}

7) The Sets ‘G’ of odd negative numbers, i.e. = {-2, -3, -4, -5, -6,……….}

Identify the finite & Infinite Set among -

Example – 1

Identify the finite & Infinite Set among the following – ‘X’ = { 2, 3, 4, 5, 6, 7, 8, 9, 10 }

Set ‘X’ has a limited number of members, so set ‘X’ is the Finite number Set.

Example – 2

Identify the finite & Infinite Set among the following -  ‘A’ = { 1, 2, 3, 4, 5, 6,……….. }

Set ‘A’ has an unlimited number of members, so ‘A’ is an Infinite number set.

Example – 3

Z = { x / x = 2n – 2 , n ϵ Z , 2 < n < 15 }

Ans.)   (2n – 2) =  2*3 – 2, 2*4 – 2, 2*5 – 2, 2*6 – 2, 2*7 – 2, 2*8 – 2 = 4, 6, 8, 10, 12, 14

So, Z = { 4, 6, 8, 10, 12, 14 }

Example – 4

‘B’ = { x / x = 2n+3, n ϵ B, 4 < n < 20 }  (n =1, 2, 3, 4, 5,……)

Ans.) 2n+3 = 2*1+3, 2*2 + 3, 2*3 + 3, 2*4 + 3, 2*5 + 3, 2*6 + 3, 2*7 + 3 = 5, 7, 9, 11, 13, 15, 17, 19

B = { 5, 7, 9, 11, 13, 15, 17, 19 }