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Math Help - [SOLVED] find second derivative

  1. #1
    Newbie reah's Avatar
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    Exclamation [SOLVED] find second derivative

    hey, i need help with this problem :

    Instructions: find d^2y/dx^2 in terms of x and y

    x^2 + y^2 = 36

    ( i can find the first derivative (y' = -x/y) but i don't understand how to get the second derivative (answer is supposedly -36/y^3)

    all help is appreciated!
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  2. #2
    MHF Contributor
    skeeter's Avatar
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    \frac{d}{dx}\left(\frac{-x}{y}\right) =

    \frac{(y)(-1) - (-x)(y')}{y^2} =

    \frac{-y + x \cdot \frac{-x}{y}}{y^2} =

    \frac{y\left(-y + x \cdot \frac{-x}{y}\right)}{y \cdot y^2} =

    \frac{-y^2 - x^2}{y^3} = -\frac{36}{y^3}
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  3. #3
    Newbie reah's Avatar
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    Thumbs up Thanks!

    Thank you so much!
    I finally get it.
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