Prove that the function 𝑓: 𝑁 → 𝑁, given by 𝑓(1) = 𝑓(2) = 1 and 𝑓(𝑥) =

This question was asked in Ex 10.2, 15

Prove that the function 𝑓: 𝑁 → 𝑁, given by 𝑓(1) = 𝑓(2) = 1 and 𝑓(𝑥) = 𝑥 − 1 for every
𝑥 > 2, is onto but not one-one.