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Homework Help: Derivatives of functions

  1. Apr 24, 2006 #1
    I need a help on this question,Show that if u=x-y,v=xy and w=f(u,v) then x[tex]\frac{dw}{dx}[/tex]-y[tex]\frac{dw}{dy}[/tex]=(x-y)[tex]\frac{dw}{du}[/tex].
     
  2. jcsd
  3. Apr 24, 2006 #2

    mathman

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    To simplify writing, I will use d for partial derivatives.

    f(u,v)=f(x-y,xy)
    df/dx=df/du+ydf/dv
    df/dy=-df/du+xdf/dv
    xdf/dx-ydf/dy=(x+y)df/du

    Note difference! (x+y) not (x-y)
     
  4. Apr 24, 2006 #3

    Hootenanny

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    Suggest moving this to Calc homework pages.

    ~H
     
  5. Apr 24, 2006 #4

    HallsofIvy

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    Done! xxxxxxxxx
     
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