So it's the derivative with respect to x of x squared plus y squared, x squared plus y squared on the left-hand side of our equation, and then that's going to be equal to the derivative with respect to x on the right-hand side. I'm just doing the same exact thing to both sides of this equation. Now, if I take the derivative of the sum of two terms, that's the same thing as taking the sum of the derivative. So this is going to be the same thing as the derivative with respect to x of x squared plus the derivative with respect to x of y squared. I'm writing all my orange stuff first. So let's see, this is going to be x squared, it's gonna be y squared, and then this is going to be equal to the derivative with respect to x of a constant. This isn't changing with respect to x.