Question

Is `(2,3),(-4,5),(-2,7),(7,7)` a function?

Answer 1

Yes.

Explanation:

If we define a function `f:{-4,-2,2,7}->{3,5,7}`, such that `f(-4)=5,f(-2)=7,f(2)=3,f(7)=7` then `f` is indeed a function.

We note that `f` is surjective in this case but not injective. Also, we could pick any number set to be the codomain of `f`, but this would make `f` non-surjective.