Instead of a parabola that just goes like this, if you were to kind of rotate it around and distort it a little bit, you would get this thing that looks kind of like a cup or a thimble or whatever. What we want to do is we want to find the m and b values that minimize. Notice this is a three-dimensional surface. I don't know if I'm doing justice to it. Let me see if I can imagine a three-dimensional surface that looks something like this. This is the back part that you're not seeing. That's the inside of our three-dimensional surface.