I sometimes complain about the quotient rule, saying, hey, it's just a variation of the product rule, but it's actually quite useful in something like this. We just have to remind ourselves that this is going to be equal to the derivative of the numerator with respect to x, and so that's just going to be derivative of y with respect to x times the denominator, three y squared minus x, minus the numerator, y, times the derivative of the denominator with respect to x. Well, what's the derivative of this denominator with respect to x? Well, the derivative of three y squared with respect to x, that's going to be the derivative of three y squared with respect to y, which is just going to be six y, I'm just using the power rule there, times the derivative of y with respect to x. All I did just now is I took the derivative of that with respect to x, which is the derivative of that with respect to y times the derivative of y with respect to x, comes straight out of the chain rule, minus the derivative of this with respect to x, which is just going to be equal to one. All of that over, remember, we're in the middle of the quotient rule right over here. All of that over the denominator squared.