And so first, on the left-hand side, we essentially are just going to apply the chain rule. First, we have the derivative with respect to x of x minus y squared. So the chain rule tells us this is going to be the derivative of the something squared with respect to the something, which is just going to be 2 times x minus y to the first power. I won't write the 1 right over there. Times the derivative of the something with respect to x. Well, the derivative of x with respect to x is just 1. And the derivative of y with respect to x, that's what we're trying to solve.