Well no, we don't know what the x sub i's are, so we just have to leave that the same. So that's the sum. Oh sorry, this is just the numerator, right? This whole simplification, we're just simplifying the numerator, and later we're just going to divide by n. So that is equal to that divided by n, which is equal to this thing divided by n. I'll divide by n at the end, because it's the numerator that's the confusing part, right? We just want to simplify this term up here. So let's keep doing this. So this is equal to the sum from i equals 1 to n of x sub i squared, and let's see, minus 2 times mu.