I'm sure the proof is really easy, but I am relatively new to these proofs and I'm not really sure how to start...

Let f: R R and let c R. Show lim as x c of f(x) = L if and only if lim x 0 of f(x+c) = L

(sorry about the code, this is the first time I have used Latex...can anyone suggest an all in one reference for Latex coding?)