So this is the derivative of this, of the first derivative right over there. And we've already seen examples of how can we identify minimum and maximum points. Obviously, if we have the graph in front of us, it's not hard for a human brain to identify this as a local maximum point. The function might take on higher values later on. And to identify this as a local minimum point, the function might take on lower values later on. But we saw, even if we don't have the graph in front of us, if we're able to take the derivative of the function, we might, or even if we're not able to take the derivative of the function, we might be able to identify these points as minimum or maximum. The way that we did it, we said, OK, what are the critical points for this function?