00:01
Okay, so derivative is 18x squared minus 18x minus 216, okay? and divide everything by 3, so you get 6x squared minus 6x minus 72.
00:23
Well, actually, we can even divide everything by 6, right? x squared minus x minus 12, so x minus 4, x plus 3, so the critical numbers are 4 and negative 3, right? and then what? evaluate the fx at the critical numbers we just...okay.
00:51
So, what we're doing here is it's a closed interval, and the closed interval, what you have to do is endpoints, which is negative 4 and 5.
01:05
And the critical points are 4 and negative 3, and they are in the interval, so we're going to go ahead and calculate these function values.
01:19
For these, i think you should use, you should definitely use a calculator.
01:26
Let's see what's going on here.
01:29
Okay, so when you put negative 4 for x, you will get 336...