So let's take the derivative of x to the n. And now that we know the binomial theorem, we have the tools to do it. So how do we take the derivative? Well, what's the classic definition of the derivative? It is the limit as delta x approaches 0 of f of x plus delta x, right? So f of x plus delta x in this situation is x plus delta x to the nth power, right? Minus f of x. Well, f of x here is just x to the n. All of that over delta x.