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Math Help - Derivatives

  1. #1
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    Derivatives

    What is the second derivative of f(x) = x-2 / x2 3x 4
    I found the first derivative which is f'(x) = -x2 + 4x 10 / (x2 - 3x 4)2

    When I solve for the second derivative I get f"(x) = (-2x + 4)(x2 - 3x 4)2 (-x2 + 4x 10)(2x - 3)2 / (x2 - 3x 4)4


    When I simplify this though and test it using graphing technology It doesn't equate. What am I doing wrong?
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  2. #2
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    Quote Originally Posted by steezin View Post
    What is the second derivative of f(x) = x-2 / x2 – 3x – 4
    I found the first derivative which is f'(x) = -x2 + 4x – 10 / (x2 - 3x – 4)2

    When I solve for the second derivative I get f"(x) = (-2x + 4)(x2 - 3x – 4)2 - (-x2 + 4x – 10)(2x - 3)2 / (x2 - 3x – 4)4


    When I simplify this though and test it using graphing technology It doesn't equate. What am I doing wrong?
    Dear steezin,

    Your the second derivative is incorrect. It should be,

     f ''(x) = \frac{(-2x + 4)(x^2 - 3x - 4)^2 - ((-x^2 + 4x - 10)\times{2}\times{{\color{red}(x^2-3x-4)}(2x-3)})}{(x^2 - 3x - 4)^4}

    Hope this will help you.
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