You can figure out what the exact value is if you like. So because this is less than zero, we are concave downwards, concave downwards. Another way of saying it is that the slope is, the slope is decreasing the entire time, concave downwards. When the slope is decreasing the entire time, our shape looks like that. The slope could start off high, lower, lower, gets to zero, even lower, lower, lower. And we even saw that on the graph right over here. And since it's concave downwards, that implies that our critical point that sits where, during where the interval is concave downward, that critical point is a local maximum, is a maximum.