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Math Help - Partial derivatives

  1. #1
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    Partial derivatives

    I'm trying to revise but I can't seem to solve this:

    Partial derivatives-eq.latex.gif

    The problem is that for 4 marks it's taken me way too long to expand and differentiate.

    Is there a shortcut that I'm missing???
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  2. #2
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    Note, for some reason the file only opens if you click on the empty space twice
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  3. #3
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    Quote Originally Posted by Roland25 View Post
    I'm trying to revise but I can't seem to solve this:

    Click image for larger version. 

Name:	eq.latex.gif 
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ID:	11329

    The problem is that for 4 marks it's taken me way too long to expand and differentiate.

    Is there a shortcut that I'm missing???
    Use the chain rule

    \frac{\partial f}{\partial u} = \frac{\partial f}{\partial x}\frac{\partial x}{\partial u}+\frac{\partial f}{\partial y}\frac{\partial y}{\partial u}+\frac{\partial f}{\partial z}\frac{\partial z}{\partial u}

    \frac{\partial f}{\partial u}=(3x^2-2xy)(1)+(-x^2-2z^2y)(1)+(-2zy^2)(0)

    From here just sub in
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