00:01
So i have y equals 3x to the fourth plus 4x cubed.
00:07
I first want to find intercepts.
00:12
X intercepts happen when your function equals 0.
00:17
So i'm going to factor out an x cubed.
00:21
That gives me 3x plus 4.
00:25
So i have x cubed is 0, 3x plus 4 is 0.
00:29
So i have 0 and negative 4 thirds.
00:34
As coordinates, that's negative 4 thirds, 0 and 0, 0.
00:40
Next i want to find relative min or max.
00:45
So i'm going to find the derivative, which is 12x cubed plus 12x squared.
00:55
I'm going to set that equal to 0 and i'm going to factor out a 12x squared.
01:01
That leaves me with x plus 1.
01:04
So i have critical values at 0 and negative 1.
01:09
I'm going to plot them on a number line.
01:12
Then i'm going to take my derivative, 12x cubed plus 12x squared.
01:22
And i'm going to choose some test points.
01:32
So if i plug in negative 2, i get out something negative.
01:38
Negative 1 half, i'm going to get out something positive.
01:42
And 1, i'm going to get out something positive.
01:48
Okay, so that tells me i'm going to have a relative min.
01:54
I'm decreasing here and then i'm increasing here.
01:57
So i'm going to have a relative minimum at negative 1...