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Math Help - Help on log derivation

  1. #1
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    Help on log derivation




    Moderator edit: Restored deleted question. Thread closed.
    Last edited by mr fantastic; November 19th 2010 at 08:02 PM. Reason: Restored original post.
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  2. #2
    MHF Contributor harish21's Avatar
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    what have you tried?


    Hint: write  x^3(x-2)^3 = (x(x-2))^3=(x^2-2x)^3

    so have \dfrac{x^3(x-2)^3}{(x^2+8)^7} = (x^2-2x)^3\; (x^2+8)^{-7}

    use the product rule!
    Last edited by harish21; November 19th 2010 at 01:32 PM.
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  3. #3
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    Quote Originally Posted by softballchick View Post



    Thanks
    Are we to assume that you're required to find the derivative by logarithmic differentiation? It isn't clear!
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  4. #4
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    If f(x)= \frac{x^3(x- 2)^3}{(x^2+ 8)^7}

    then ln(f(x))= 3 ln(x)+ 3ln(x- 2)- 7 ln(x^2+ 8)

    So that \frac{1}{f(x)}\frac{df}{dx}= the derivative on the right.

    To find \frac{df}{dx} differentiate on the right and multiply by f(x)= \frac{x^3(x- 2)^3}{(x^2+ 8)^7}.
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  5. #5
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    thanks I got it!
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  6. #6
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    Quote Originally Posted by softballchick View Post
    thanks I got it!
    1. Be clear as to what you mean next time so as not to waste people's time.
    2. Editing out posts after getting help isn't allowed, and it's a sign of cheating.
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