# Thread: More chain rule problems

1. ## More chain rule problems

Ok, Here is another calculus problem to check. Can someone tell me if I done this one correctly.

2. Originally Posted by robasc
Ok, Here is another calculus problem to check. Can someone tell me if I done this one correctly.
You have a product, and both factors contain $x.$ Isn't there a certain rule you should be using here? ...for the product? Go to it.

3. Originally Posted by robasc
Ok, Here is another calculus problem to check. Can someone tell me if I done this one correctly.

product rule and chain rule ...

$f(x) = x(3x-9)^3$

$f'(x) = x \cdot 3(3x-9)^2 \cdot 3 + (3x-9)^3 \cdot 1$

$f'(x) = 9x(3x-9)^2 + (3x-9)^3$

$f'(x) = (3x-9)^2[9x + (3x-9)]$

$f'(x) = (3x-9)^2(12x-9)$