This is just going to be a ton of algebraic manipulation, but I'll try to color-code it well so we don't get lost in the math. Let me just rewrite this expression over here. This whole video is just going to be rewriting this over and over again, just simplifying it a bit with algebra. This first term right over here, y1 minus mx1 plus b squared, that's going to be, and we could write this as all going to be the squared error of the line. This first term over here, I'll keep it in blue, is going to be, if we just expand it, y1 squared minus 2 times y1 times mx1 plus b plus mx1 plus b squared. All I did is I just squared this binomial right here. You can imagine this, if this was a minus b, it would be a squared minus 2ab plus b squared.