Delta equals function of epsilon that is defined for any positive epsilon. You give me an epsilon, I just put it into our little formula, our little function box, and I will always get you a delta. If I can do that for any epsilon, that will always give you a delta where this is true, that if x is within that range of delta of c, then the corresponding f of x is going to be within epsilon of l, then the limit definitely exists. Let's try to do that. Let's think about being within delta of our c. Let's think about this right over here as 5 plus delta. This is 5 minus delta. That's our range we're going to think about.