00:01
To find the critical numbers, we'll take the derivative, and we're going to set this equal to zero in just a minute.
00:07
So this would give us 4x cubed plus 12x squared, and then the derivative of a constant is 0.
00:19
So now setting this equal to 0 and factoring out the greatest terms that we can on the right side would be a 4 and an x squared.
00:30
So that would leave us with an x, and then plus the first.
00:36
So there's two critical points here.
00:41
X is 0 and x is negative 3.
00:47
And these are when we have slopes of 0, so they'll help us determine at what points basically we turn around from going increasing to decreasing, we're decreasing to increasing here.
01:00
So we'll set up our interval at these two values, negative 3 and 0.
01:10
And first we'll find intervals of increasing, decreasing by using some test values, such as negative 4, negative 2, or positive 1.
01:22
And we'll plug these into the factored derivative...