And our left-hand side is exactly what we eventually wanted to get. So the second derivative of y with respect to x. And what do we get here on the right-hand side? Well, we can apply the product rule. So first, we can say the derivative of x with respect to x, well, that is just going to be one times the other thing. So times y to the negative one power, y to the negative one power. And then we have plus x times the derivative of y to the negative one.