00:01
So we're looking at the function defined as 12x cubed minus 99x squared minus 720x plus 6.
00:13
And we need to find the derivative of this.
00:15
It's just going to be our power rule.
00:18
Like 12 times 3 is 36.
00:20
You subtract 1 from the exponent.
00:23
99 times 2 is 198.
00:26
You subtract 1 from the exponent minus 720.
00:31
And the critical numbers will happen if that equals 0.
00:34
Now let's see if all these numbers are divisible by...
00:37
Maybe they're all divisible by 18.
00:40
See i think you can factor out an 18 there.
00:43
2x squared would be 11x when i divide.
00:47
And 720 divided by 18 is 40.
00:52
And i'm going to try and factor this.
00:54
So there's only one way of getting 2x squared.
00:56
That's 2x times x.
00:58
But then thinking about all the different ways you can get 40.
01:02
I'm just trying to ponder because it'd be like 80.
01:07
And let's see is 80 divisible by 4? but that's not going to work for me.
01:14
80 divisible by...
01:19
I want to say it's going to be 5 and 16.
01:27
And the only way to get the 16 is if you did 2 times 8.
01:32
And that's negative 16...