1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Derivative question?

  1. Oct 6, 2008 #1
    1. The problem statement, all variables and given/known data
    Find the derivative of: cube root of (1/(2-3x))

    2. Relevant equations
    use chain rule (i think?):(f of g)'(x) = f'(g(x))*g'(x)

    3. The attempt at a solution
    first, i changed the cube root to the exponent 1/3.
    second, i did the derivative and came up with 1/((1/(2-3*x))^(2/3)*(2-3*x)^2)
    now i think i need to cancel out the 1/(2-3*x))^(2/3), but i'm not sure how to go about it.
    ---i kinda cheated and went on maple to see if my answer was close, and it came up as 1/(9*x^2-12*x+4), and i knew i had to factor the last part of the denominator, but i don't understand how the first part of the denominator disappeared.

    thanks for all of your help!
  2. jcsd
  3. Oct 6, 2008 #2


    User Avatar
    Science Advisor
    Homework Helper

    Your answer is more correct than maple's answer. Are you sure you typed it in correctly? You should get 1/(2-3x)^(4/3). 2-2/3=4/3. Sure you can't see how the exponents add up to that?
  4. Oct 7, 2008 #3
    yeah, i guess that makes sense. the division signs in the equation tend to confuse me. i'll have to do some more problems before i get the hang of it. it's still pretty confusing.
    i must've used maple wrong. i've only started using it the past week. it seems like i need a degree just to understand how to use it :)
    Thank you for the help!!!
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook