And then if we look at every term here, every term in the numerator has a delta x, right? So we can divide the numerator and the denominator, essentially, by delta x. This is the same thing as 1 over delta x times this whole thing. So that is equal to, let me, the limit as delta x approaches 0 of, so we divide the top and the bottom by delta x, or we multiply the numerator times 1 over delta x, we get n choose 1 x to the n minus 1. What's delta x divided by delta x? Well, that's just 1, right? Plus n choose 2 x to the n minus 2.