00:01
Okay, so i am going to find f prime of x, which is the derivative of this function.
00:08
This function is a product, so i'm going to use product rule, which says i want the first function, which is x, times the derivative of the second.
00:20
Well, the second is the 4 minus x quantity cubed, and that is a chain rule.
00:26
So i'm going to drop that three down in front.
00:28
I have 4 minus x squared times negative 1 plus the second function times the derivative of the first, which is just x.
00:47
Okay, let's clean that up a little bit before we plug in our number.
00:52
So we have x times 3 times negative 1, so that's negative 3x times 4 minus x squared, plus one times anything is just itself.
01:06
I have 4 minus x cubed.
01:11
Now i can take out a 4 minus x factor.
01:16
Actually, i can take out two of them because that's common to both of these terms.
01:22
And that is going to leave me with, when i take that out, negative 3x plus, and then i just have one, four minus six.
01:33
X almost done cleaning up 4 minus x quantity squared times let's see that's negative 3x and negative x negative 4x plus 4 okay so here's my derivative now i want to write an equation of a tangent line so what do i need for an equation i need a point and i need slope all right so i have the x coordinate to my point.
02:18
I need to go and get the y coordinate by plugging two into the original function...