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Find concave up and down

  1. Nov 22, 2012 #1
    1. The problem statement, all variables and given/known data

    f(x)=(2x)/((x^2)-25)

    find concave up and down

    2. Relevant equations



    3. The attempt at a solution

    I found the second derivative to b

    -4x((-2x^2)-24)
    -----------------
    ((x^2)-25)^2

    i found the only inflection point was x=0 (which was correct)

    I plugged in values on both the right and left side of 0 and determined that f(x) was concave down on all values smaller than 0 with the exception of -5, and f(x) was concave up on all values larger than 0 with the exception of 5

    however this is not the correct answer. Can someone confirm/tell me what i am doing wrong?

    thanks
     
    Last edited: Nov 22, 2012
  2. jcsd
  3. Nov 22, 2012 #2

    LCKurtz

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    Something is wrong with your calculations as that is not correct for the second derivative.
     
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