So it's defined everywhere, so let's just figure out where it's equal to 0. So f prime of x is equal to 0. So let's solve which x is, so let's solve, well I don't have to rewrite that, I just wrote that. Let's solve for whether this is equal to 0, and I'll do it in the same color. So 12x to the 3rd minus 12x squared is equal to 0. And so let's see what we can do, what can we do to solve this. Well we could factor out a 12x.