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Homework Help: Finding Derivative, but wrong sign

  1. Nov 4, 2005 #1
    Ok, Im doing my calculus homework, but sometimes I get a negative in the wrong place...
    Here is an example:
    The solution I got for the derivative attached is on the numerator:
    5e^x(9e^x)-5e^x(4+9e^x)
    In the solution, the negative sign is on the other side??
    I dont get it
     

    Attached Files:

  2. jcsd
  3. Nov 4, 2005 #2

    Tom Mattson

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    Staff Emeritus
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    Gold Member

    You are probably misapplying the quotient rule, which is:

    [tex]\frac{d}{dx}\left(\frac{f}{g}\right)=\frac{f'g-fg'}{g^2}[/tex]

    It does matter in which order you place the terms in the numerator.
     
  4. Nov 4, 2005 #3
    Damn!
    I didnt know that! Thanks a lot man!
     
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