And notice, this is exactly, this is exactly what we have over here. That is n times the mean of the squared values of y or the mean of the y squareds. That's exactly what that is and we can do that with each of these terms. What is, what is x1, x1, y1 plus x2, y2 plus all the way to, all the way to xn, yn. Well if we take this whole sum and we divide it by n terms, this is going to be the mean value for x times y. For each of those points, you multiply x times y and you find the mean of all of those products. That's exactly what this is.