1. The problem statement, all variables and given/known data Let (X,d) and (Y, p) be metric spaces and f : X -> Y a function. Prove that f is continuous at p-0 if and only if for every ε > 0, there exists a δ > 0 so that the image of Bd(p-0; δ) is contained in Bp( f (p-0);ε). 2. Relevant equations 3. The attempt at a solution For the forward implication, I feel like I am almost there. The statement f is continuous at p-0 implies for every e>0 there is a delta>0 so that when d(p, p-0)< delta this implies p( f(p), f(p-0))<e. But d(p, p-0)< delta implies x is contained in B (sub d) (p-0; delta) and p( f(p), f(p-0))<e implies f(p) is contained in B (sub p) (f(p-0); e). Here is where I would like to say that notice that the image of x is contained in f(x). Then I can conclude that the image of B (sub d) is contained in B (sub p) Then, I was going to reverse it for the other implication.