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Math Help - Derivative Help

  1. #1
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    Derivative Help

    find y' if y=x/(x+y)

    Do you take the derivative of the y on the left of the = or no?

    I really need help
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  2. #2
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    Quote Originally Posted by rawkstar View Post
    find y' if y=x/(x+y)

    Do you take the derivative of the y on the left of the = or no?

    I really need help
    to make it a bit easier, multiply both sides by (x+y) to clear the fraction ...

    y(x+y) = x

    xy + y^2 = x

    now take the derivative implicitly ...

    xy' + y + 2y \cdot y' = 1

    xy' + 2y \cdot y' = 1 - y

    y'(x + 2y) = 1 - y

    y' = \frac{1-y}{x+2y}
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