That's when you divide it by 2n, you get this. And when you divide this by 2n, that'll go away, that will go away, and then those will go away. And you're just left with negative, the negative mean of the y's, plus m times the mean of the x's, plus b is equal to 0. So if we find the m and the b values that satisfy the system of equations, we have minimized the squared error. And we could just solve it in a traditional way, but I want to rewrite this, because I think it's kind of interesting to see what these really represent. So let's add this mean of the x, y's to both sides of this top equation. And then we're going to have, so if we add the mean of the x, y's to both sides of this top equation, what do we get?