So just to show you that, what is, if I want to take the mean of all of the squared values of the y's. So that would be this, that would be y1 squared plus y2 squared plus all the way to yn squared. So I've summed n values, n squared values and then I want to divide it by n, since there are n values here, and this is the mean of the y's squared. That's how we can denote it just like that. That is the mean of the y squared. Or if you multiply both sides of this equation by n, you get y1 squared plus y2 squared plus all the way to, all the way to yn squared, yn squared is equal to n, is equal to n, let me do this in different colors, is equal to, so this is, this is equal to n, this n times the mean of the squared values of y. And notice, this is exactly, this is exactly what we have over here.