I have a question here that asks:

Let S = {1, 2, 3, 4, 5} and define f : S --> Z by

f(x) = {x² + 1 if x is even

{2x - 5 if x is odd

(the 2 brackets are meant to be one big bracket)

Express f as a subset of S x Z. Is f one-to-one?

I am very unsure as to where to even start with this question, any help would be greatly appreciate. Thanks a lot.