I know it's confusing with me saying sub i and all of that, but it's really no different than when you did a minus b squared, just the variables look a little bit more complicated. And then the last term is minus mu times minus mu, which is plus mu squared. Fair enough. Let me switch colors, just to keep it interesting. Let me cordon that off. OK, so how can we, well, the sum of this is the same thing as the sum of, because you think about it, we're going to take each x sub i, for each of the numbers in our population, we're going to perform this thing, and we're going to sum it up. But if you think about it, this is the same thing as, if you're not familiar with sigmation, this is a good kind of thing to know in general, just a little bit of intuition, that this is the same thing as, I'll do it here to have space, as the sum from i is equal to 1 to n of the first term, x sub i squared minus, and actually we can bring out the constant terms.