But let's keep going and let's try to understand the concativity and maybe we can get a better sense of this graph. So let's figure out the second derivative. So the second, I'll do that in, let me do it in this orange color. So the second derivative of my function f, let's see, 3 times 12 is 36x squared minus 24x. So let's see, well there's a couple of things we can do. Now that we know the second derivative, we can answer the question, is my graph concave upwards or downwards at either of these points? So let's figure out what, at either of these critical points.