I need to give examples of functions mapping from the natural numbers into the natural numbers with the following properties:
1. Surjective, not injective
2. Injective, not surjective
f(x) = 2x
3. Neither injective nor surjective
4. Bijective
f(x) = x
I think I figured out (2) and (4) but any help with the other two conditions would be helpful!