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Math Help - Derivative of a function

  1. #1
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    Derivative of a function

    Hi!
    Usually in class there are examples when you are able to find these derivatives by derivativating both sides and at the end you can simply cross out some parts and get y' simply by dividing.
    In this example I can't figure out what to do next:
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    I don't ask to do all the work, leave some for me too
    This is as far as I got, maybe I made a mistake so now can't see anything to divide.
    Any ideas?

    [EDIT]
    Found one mistake, but doesn't change much, not (x+y)^2 but (x-y)^2
    Last edited by regdude; October 17th 2011 at 01:17 PM.
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  2. #2
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    Re: Derivative of a function

    Quote Originally Posted by regdude View Post
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    I don't ask to do all the work, leave some for me too
    This is as far as I got, maybe I made a mistake so now can't see anything to divide.
    I would rewrite it as:
    \left( {x^2  + \frac{{2y}}{{x^2  + y^2 }} + \frac{2}{{1 + (x + y)^2 }}} \right)y' = \frac{2}{{1 + (x + y)^2 }} - \frac{{2x}}{{x^2  + y^2 }} - 2xy

    Solve for y'.
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  3. #3
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    Re: Derivative of a function

    Aww... I forgot that you can write (a+b)/c = a/c + b/c
    Thanks!
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