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Homework Help: Derivative of Fraction using power rule

  1. Oct 2, 2011 #1
    The problem:
    f(x)=3-3/5x

    So I'm perfectly fine with finding the derivatives with stuff but I wasn't sure about this one. Would this be 0 because there is a three in the numerator and no x?
    Or would it be 3-1/51-1=3-1=2?
     
  2. jcsd
  3. Oct 2, 2011 #2
    Sorry, is that [itex] f(x) = 3 - \frac35 x[/itex] or [itex] f(x) = 3 - \frac3{5x} [/itex]?
     
  4. Oct 2, 2011 #3
    f(x)=3−3/5x
    The derivative of 3 is going to be zero because its a constant.
    Bring the x to the numunator.

    Then you get 3x^-1/5. Apply the power rule
    You get:

    (-1)3x^-1-1/5 = -3x^-2/5

    Now rewrite with postive exponants:

    f'(x)= 3/5x^2
     
  5. Oct 2, 2011 #4
    Thanks, that was pretty easy!
     
  6. Oct 2, 2011 #5
    Hi Windowmaker. The point of these forums is to help guide people to the solution, not to do it for them.
     
  7. Oct 2, 2011 #6
    I aplogize, im new here. I wont make that mistake in the future!
     
    Last edited: Oct 2, 2011
  8. Oct 2, 2011 #7
    No problem. I made that mistake when I was new too. Have fun and enjoy the forums.
     
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