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Math Help - Second Derivative

  1. #1
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    Second Derivative

    Find the second derivative:

    f(x)=x/(x^2+1)

    Thanks guys
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  2. #2
    Grand Panjandrum
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    Quote Originally Posted by c_323_h View Post
    Find the second derivative:

    f(x)=x/(x^2+1)

    Thanks guys
    I expect you are meant to use the quotient rule to do this, but since
    I don't lnow it I will use the product rule:

    df/dx= 1/(x^2+1) + x (-1)(2x)/(x^2+1)^2 = (x^2+1-2x^2)/(x^2+1)^2

    .............= (1-x^2)/(x^2+1)^2

    so:

    d^2f/dx^2 = -2x/(x^2+1)^2 + (1-x^2) (-2) (2x)/(x^2+1)^3

    ..............= [-2x(x^2+1)=4x+4x^3]/(x^2+1)^3

    ..............= [2x(x^2=3)]/(x^2+1)^3

    RonL
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  3. #3
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    thanks. i liked the old MHF better. what happened to latex
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  4. #4
    Forum Admin topsquark's Avatar
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    Quote Originally Posted by c_323_h View Post
    thanks. i liked the old MHF better. what happened to latex
    Oh it's the same forum. LaTeX wasn't part of the last update and they are working on it. They're evidently having some sort of problem with it. It'll be back at some point and then the glory will return.

    -Dan
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