Question

Prove that the function f: N → N: f(x) = 3x is one-one and into.

Answer 1

We know that

f (x₁) = f (x₂)

So we get

3x₁ = 3x₂ => x₁ = x₂

Here, f is one-one

Consider the number 2 in co domain N which has no natural image as 2

Here, f is onto.