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: Simple Derivative Question

  1. May 30, 2012 #1
    I am having trouble with this derivation: f(q)=q(Q-q). We want to find the values that maximize the vaule of q so the book sets the derivative equal to 0 and gets Q-2q=0

    When I try to do the derivative of f(q)=q(Q-q), I used the product rule

    1(Q-q) + q(Q-1)=0
    Q-q+Qq-q=0
    Q+Qq-2q=0

    I have an extra (Qq) I don't know how to get rid of.
     
  2. jcsd
  3. May 30, 2012 #2

    Mark44

    Staff: Mentor

    There's a mistake above. d/dq(Q - q) = -1, not Q - 1. Q is a constant in this function.
     
  4. May 30, 2012 #3
    ah, too many q's running around. Thank you
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook