We're going to do it for the third, x3, y3, keep going, keep going, all the way until we get to this nth term over here. This nth term over here when we square it is going to be yn squared minus 2yn times mxn plus b plus mxn plus b squared. Now the next thing I want to do is actually expand these out a little bit more. Let's expand these out a little more. Let's actually scroll down. This whole expression, I'm just going to rewrite it, is the same thing as, and remember this is just a squared error of the line, so let me rewrite this top line over here. This top line over here is y1 squared.