So I could take the derivative of the left-hand side with respect to x, and the derivative of the right-hand side with respect to x. And so what is this going to be? On the left-hand side, the notation would just be the second derivative of y with respect to x. And then over here, let's take the derivative of each of these with respect to x. The derivative of two x with respect to x is going to be equal to two, and then minus the derivative of y with respect to x was just going to be minus the derivative of y with respect to x. And so we could say, okay, we found the second derivative, but remember, they're saying in terms of x and y, right now I found the second derivative in terms of, well, in terms of a constant and in terms of the first derivative. And so we can substitute our expression for the first derivative back here to have this expression in terms of x and y.