This isn't changing with respect to x. So we just get zero. Now, this first term right over here, we have done many, many, many, many, many times. The derivative with respect to x of x squared is just the power rule here. It's going to be two times x to the first power, or we could just say two x. Now, what's interesting is what we're doing right over here. The derivative with respect to x of y squared.