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Implicit differentiation

  1. Jul 22, 2008 #1
    so I have a implicit diffentiation problem and was wondering if someone could help me out.. I need to figure out how to get

    dy/dx=0

    so eg if i had

    dy/dx = 4xy+2x/5y^2

    and you want to write this in terms of y, how is this done? is there a trick?
     
  2. jcsd
  3. Jul 22, 2008 #2

    arildno

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    Well, if dy/dx is to be 0, it follows that:
    [tex]x(4y+\frac{2}{5y^{2}})=0[/tex]
    Having as possible solutions that either x=0, or [tex]y=-\frac{1}{\sqrt[3]{10}}[/tex]
     
  4. Jul 22, 2008 #3
    thanks for your help, but im still not too sure how this works so how about with this example

    1-2x/4+2y = 0
     
  5. Jul 22, 2008 #4

    arildno

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    Well, then along the line y=x/4-1/2, dy/dx will equal zero.
     
  6. Jul 22, 2008 #5
    ah right thanks, its just i'm trying to figure out in my notes what steps my lecturer took to get x=1/2.. and i cant see how he's done it..
     
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