So we can say, and I'll switch colors here, that f has critical points at x equals 2 and x equals negative 2. Well, that's fair enough. But we still don't know whether the function takes on minimum values at those points, maximum values at those points, or neither. To figure that out, we have to figure out whether the derivative changes signs around these points. So let's actually try to graph the derivative to think about this. So let's graph. So I'll draw an axis right over here.