1. Contradiction Proof- injection, Infinite Sets

Suppose that there is an injection f: Z+->X. Prove by contradiction that x is an infinite set.

2. Originally Posted by Laurali224
Suppose that there is an injection f: Z+->X. Prove by contradiction that x is an infinite set.
The solution depends on two things.
What are you using for the definition of infinite set?
What other theorems do you have to use?

I will say that proof by contradiction of this likely uses the fact that the composition of two injections is an injection.