Derivative of x to the fourth is four x to the third, so that looks right. All of this looks algebraically right. And let's see, when you simplify this, so let's see, x to the negative 1 1⁄2 times x to the fourth is indeed x to, well, that's going to be x to the, oh, this correlates, so this simplifies to that, which looks correct, and that simplifies to that, which looks correct. We're just using exponent properties there. And then divided everything by, let's see, oh, then everything is in terms of x to 3.5, so we're going to have negative 3.5 x to 3.5, and then you use exponent properties. So actually, it looks like he did everything correctly. This is the right answer.