So let me write it that way. So this is also equal to two minus two x plus y. So that's everything we know before we even thought that maybe there's a solution of y equals mx plus b. So now let's start with y equals mx plus b. So if y is equal to mx plus b, y equals mx plus b, so this is the equation of a line, then dy dx is going to be equal to, well the derivative of this with respect to x is just m, derivative of this with respect to x, it's a constant, it's not going to change with respect to x, it's just a zero. And that makes sense. The rate of change of y with respect to x is the slope of our line.