So we know that, we know that dy over dx is equal to two x minus y. They told us that. We also know that the second derivative, the second derivative of y with respect to x is equal to two minus dy dx. We figured that out in part b of this problem. And then we could also express this, we saw that we could also write that as two minus two x plus y if you just substitute, if you substitute this in for that. So it's two minus two x plus y. So let me write it that way.