Let A = {1, 2, 3}

TIP: – One – One Function: – A function is said to be a one – one functions or an injection if different elements of A have different images in B.

So, is One – One function

⇔ a≠b

⇒ f(a)≠f(b) for all

⇔ f(a) = f(b)

⇒ a = b for all

We have A = {1, 2, 3}

So all one – one functions from A = {1, 2, 3} to itself are obtained by re – arranging elements of A.

Thus all possible one – one functions are:

f(1) = 1, f(2) = 2, f(3) = 3

f(1) = 2, f(2) = 3, f(3) = 1

f(1) = 3, f(2) = 1, f(3) = 2

f(1) = 1, f(2) = 3, f(3) = 2

f(1) = 3, f(2) = 2, f(3) = 1

f(1) = 2, f(2) = 1, f(3) = 3