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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!!
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