Let A and B be subsets of the setZof all integers, and let F denote the set of all functions f : A--> B. Define a relation R on F by: for any f,g F, fRg if and only if f-g is a constant function; that is, there is a constant c so that f(x) - g(x) = c for all x A.

I need to prove that R is an equivalence relation on F.