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. Then I'm going to distribute this 2y1. This is going to be minus 2y1mx1, that's just that times that, minus 2y1b and then plus, and now let's expand mx1 plus b squared. That's going to be m squared x1 squared plus 2 times mx1 times b plus b squared.