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Math Help - Math Helpp

  1. #1
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    Math Helpp

    Find the value of the second derivative when x = 20 for
    the following function:

    f(x) = 200x divided by (x+40)
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  2. #2
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    did you find the first derivative?
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  3. #3
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    f(x) = 200x divided by (x+40)

    => f(x) = \frac{200x}{x+40}

    => f'(x) = \frac{200(x+40)-1*200x}{(x+40)^2}

    ...

    => f''(x) =
    Last edited by Rapha; November 18th 2008 at 08:44 PM.
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  4. #4
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    Quote Originally Posted by Rapha View Post
    f(x) = 200x divided by (x+40)

    => f(x) = \frac{200x}{x+40}

    => f'(x) = \frac{200(x+40)-1*200x}{(x+40)^2}

    ...

    => f''(x) =
    why didn't you simplify f'(x) ?

    f'(x) = \frac{200(x+40)-1(200x)}{(x+40)^2}

    f'(x) = \frac{200x + 8000 - 200x}{(x+40)^2}

    now finish the algebra clean-up for f'(x) and find f''(x).
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  5. #5
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    Quote Originally Posted by skeeter View Post
    why didn't you simplify f'(x) ?
    i think it is his business, because simplify f'(x) is duck soup, isn't it?
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