So this is looking good. Second derivative, we take this, multiply this times 1 3rd, which would be negative 2 9ths, and then decrement negative 2 3rds, which would indeed be negative 5 3rds. So that looks right. And then it looks like Robert's trying to rewrite it. So we have the negative 2 9ths still. But then he recognized that this is the same thing as x to the 5 3rds in the denominator. And x to the 5 3rds is the same thing as x, as the cube root of x to the 5th.