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: Absolute Maximum/Minimum Help

  1. Mar 22, 2010 #1
    1. The problem statement, all variables and given/known data
    (16x)/(x^2+4) for -5 (less than OR equal to) x (less than OR equal to) 5


    2. Relevant equations
    Set the derivative of the equation equal to 0, solve for x to find the critical points, then plug and check for validity.


    3. The attempt at a solution
    I used product rule for (16x)*(x^2+4)^-1

    I got the derivative as
    (-32x^2)/((x^2+4)^2) + (16/(x^2+4))
    which I then set equal to 0.

    I then made an attempt to solve for x, but got x^2(48x^2+256)=-256, which I'm very unsure of, and am also not sure how to solve.
    Help is appreciated.
     
    Last edited: Mar 22, 2010
  2. jcsd
  3. Mar 22, 2010 #2
    You have made an error while solving your equation. Try to write your original derivative as a single fraction and I hope it would be more clear then what to solve.
    (Your final equation gives complex solutions which shouldn't be the case ;) )
     
  4. Mar 22, 2010 #3
    I see now!!! I really need to get more comfortable with the quotient rule. I think I end up running myself in circles too often because I try to use the product rule, and then can't alter the problem to look like it would, if I had used the quotient rule.

    Thank you very much!!
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook