So it's a closed interval. It also includes 1 and it includes 4. You can view this as the domain of our function as we have defined it. So given this, given this information, this function definition, what I would like you to do is come up with the absolute maximum value of f. Where f is defined right over here, where f is defined on this closed interval. I encourage you to pause this video and think about it on your own. So the extreme value theorem tells us, look, if we've got some closed interval, I'm going to speak in generalities here, so let's say that's our x-axis. And let's say we have some function that's defined on a closed interval.