Types of set ( null/ void / empty)

 Types of set

1) null / void / empty set

=> If number of elements in a set are zero , it is called a null set.

It is represented by:-

i) { } or

ii) ɸ (phi)

Example: 

a) A={x: x∊R , x²+ 1 =0}, there is no such value of x such that x^2 + 1 = 0

b) cardinal number of null set is 0.