The only variable when we take the partial derivative with respect to m that matters is the m. So this is a constant, there's no m here. This term right over here, we're taking with respect to m. So the derivative of this with respect to m is negative 2, it's kind of the coefficients on the m. So negative 2 times n times the mean of the xy's, that's the partial of this with respect to m. And then this term right here, this term right here has no m's in it, so it's constant with respect to m, so it's partial derivative with respect to m is 0. Then this term here, you have n times the mean of the x squared times m squared. So this is going to be, we're taking the partial derivative with respect to m, so it's going to be 2 times, so it's going to be plus 2 times, 2 times n times the mean of the x squared times m, right? The derivative of m squared is 2m, and then you just have this coefficient there as well. Now this term, you also have an m over there, so let's see. Everything else is just kind of a coefficient on this m, so the derivative with respect to m is 2bn times the mean of the x's.