# derivative problem

• Mar 3rd 2010, 09:07 PM
tbenne3
derivative problem
Given f(x) = (x^3-2x)/sqrt(2x+1) find f'(x)

I can do the first step but then I'm stuck.. Can't wait to fail my test friday.
• Mar 3rd 2010, 09:09 PM
Drexel28
Quote:

Originally Posted by tbenne3
Given f(x) = (x^3-2x)/sqrt(2x+1) find f'(x)

I can do the first step but then I'm stuck.. Can't wait to fail my test friday.

Is this a multi-stepped problem?
• Mar 3rd 2010, 09:33 PM
tbenne3
Quote:

Originally Posted by Drexel28
Is this a multi-stepped problem?

Don't know.. If I give you the answer could you figure it out?
• Mar 3rd 2010, 09:34 PM
experiment00005
Just use the quotient rule, taking the chain rule into consideration. Are you still stuck after that? I'm not sure what 'step' you're on in your solution. ^^
• Mar 3rd 2010, 09:41 PM
tbenne3
Quote:

Originally Posted by experiment00005
Just use the quotient rule, taking the chain rule into consideration. Are you still stuck after that? I'm not sure what 'step' you're on in your solution. ^^

Hmm.. I thought all I would need to do is the quotient rule.. Why does the chain rule need to be applied to?
• Mar 4th 2010, 04:03 AM
HallsofIvy
The square root: $\displaystyle \sqrt{f(x)}= (f(x))^{1/2}$ so, by the chain rule, its derivative is $\displaystyle (1/2)(f(x))^{-1/2}f'(x)$.
• Mar 9th 2010, 04:47 AM
mr fantastic
Quote:

Originally Posted by tbenne3
Given f(x) = (x^3-2x)/sqrt(2x+1) find f'(x)

I can do the first step but then I'm stuck.. Can't wait to fail my test friday.