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Derivative of (50t)/(6+t)^3

  1. Oct 5, 2012 #1

    939

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

    I keep getting it wrong. Using the quotient rule.

    2. Relevant equations

    Derivative of (50t)/(6+t)^3


    3. The attempt at a solution

    My answer: -100t^3 - 900t^2 + 10800/((6+t)^3)^2)
    The book: (-100 (t - 3))/(6 + t)^4

    What happened?



    EDIT: Nevermind, I realize they're basically the same. I'll leave this here incase someone needs help in the future.
     
    Last edited: Oct 5, 2012
  2. jcsd
  3. Oct 5, 2012 #2

    jedishrfu

    Staff: Mentor

    how did you arrive at your answer? did you use the product rule?

    with y=u v then dy/dx = du/dx .v + u . dv/dx

    i get the book answer
     
  4. Oct 5, 2012 #3

    Mark44

    Staff: Mentor

    To get the book's answer, don't multiply things out in the numerator after you use the quotient rule. In the numerator, both terms have a factor of 50 and a factor of (6 + t)2. Bring out these factors, and what you have left is easy to simplify, and results in the book's answer.
     
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