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Homework Help: Derivatives with Quotient Law Help

  1. Mar 3, 2013 #1
    Derivatives with Quotient Law Help!!

    I have a test tomorow, any help is much appreciated!! :)

    1. The problem statement, all variables and given/known data

    Dervive using the quotient rule:

    [(2-x)^3] / [(x+1)^2]

    My attempt:

    = [(x+1)^2 (3(2-x)^2)]-[(2-x)^3 2(x+1)]

    When I try expanding I get the wrong answer. The final answer's:

    [(2-x)^2 (-x-7)] / (x+1)^3

    Thankyou in advance!!
  2. jcsd
  3. Mar 3, 2013 #2


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    Staff Emeritus
    Science Advisor
    Gold Member

    For the red part, you missed a step! You need to use the chain rule on this, so you need to mulitply by the derivative of the "inside" function (which is 2-x). Also, you forgot the part in the denominator for the quotient rule!
  4. Mar 3, 2013 #3
    Ohhhh that makes so much sense!! Thank you!! :)
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