This term right here is n times the mean of the y squared values. This term right here is, I'll do it all in this green color, is equal to negative 2m, that's just that right there, times n times the mean of the xy values, the arithmetic mean. And then we have this term over here. I think you can appreciate this is simplifying the algebraic expression a good bit. This term right over here is going to be minus 2b, minus 2bn, times the mean of the y values. And then we have plus, we have this term right here, plus m squared times n times the mean of the x squared values. And then we have, almost there, home stretch, we have this over here which is plus 2mb times n times the mean of the x values.