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Homework Help: Differentiation check ?

  1. Nov 29, 2006 #1
    I should know this, but i just wanted to check....differentiating ln(3y-2z) with respect to z...............does this = -1/2z ???
     
  2. jcsd
  3. Nov 29, 2006 #2
    You must differentiate the whole thing first, then differentiate what is on the inside.

    To check your answer take the integral of -1/2z, you will see it is not equal ln(3y-2z)
     
  4. Nov 29, 2006 #3

    radou

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    As KoGs suggested, an appropriate use of the chain rule should do just fine.
     
  5. Nov 29, 2006 #4
    ok so is it -2/3y + z
     
  6. Nov 29, 2006 #5

    radou

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    No, it is not. As mentioned before, try to apply the chain rule:http://mathworld.wolfram.com/ChainRule.html" [Broken]
     
    Last edited by a moderator: May 2, 2017
  7. Nov 29, 2006 #6
    I did apply it............this is how i calculated that result:

    d/dz In(3y-2z)
    y=In u therefore dy/du = 1/u
    u=3y-2z therefore du/dz = -2
    dy/du x du/dz = -2/(3y-2z)

    where am i going wrong?
     
  8. Nov 29, 2006 #7

    radou

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    Now you're not going wrong, since the result is correct. Good work! :wink:
     
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