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Homework Help: Partial derivative

  1. Apr 17, 2007 #1
    1. The problem statement, all variables and given/known data

    Compute dv/dx and for v = [12xy-(x^2)(y^2)]/[2(x+y)]

    3. The attempt at a solution

    I attemptet to solve this problem just reading over partial derivatives for the first time and get the following answer:

    dv/dx (6y-xy^2)/(x+y)^2

    let's say I take out the numerator and just took the partial derivative of it: i.e


    would the partial derivative be = 12y-2xy^2 ?

    the book however gives the following answer without going through any steps because it is part of a larger problem.

    dv/dx = [(y^2)(12-2xy-x^2)]/[2(x+y)^2]

    I am confused because this answe is very different from mine and I can't trace my steps where I messed up.

    Please help!
    Last edited: Apr 17, 2007
  2. jcsd
  3. Apr 17, 2007 #2

    Gib Z

    User Avatar
    Homework Helper

    You have the derivative of the numerator correct. The denominators derivative is just 2. Use the quotient rule. [tex](\frac{u}{v})'=\frac{u'v-v'u}{v^2}[/tex]

    Show us your working
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