And once again, review the binomial theorem if this looks like Latin to you and you don't know Latin. n choose 1 of x to the n minus 1 delta x plus n choose 2 x to the n minus 2 delta x squared. And then plus, and we have a bunch of digits. And in this proof, we don't have to go through all the digits, but the binomial theorem tells us what they are. And of course, the last digit, we just keep adding, is going to be 1, well, it would be n choose n, which is 1. Let me just write that down. n choose n is going to be x to the 0 times delta x to the n. So that's the binomial expansion.