And let's divide that by our change in x. If this is x plus h and this is just x, our change in x is just going to be h. So that's where we get that term from. So this is just a slope between these two points. But of course, we want to find the limit as this point gets closer and closer to this point, as this point gets closer and closer to that point. So this becomes a tangent line. So we're going to take the limit as h approaches 0. And this is our f prime of x.