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Derivative not correct for online hw submission, but is correct

  1. Feb 7, 2013 #1
    1. The problem statement, all variables and given/known data
    Find the d/dx
    (x^2+2x+5)^2


    2. Relevant equations


    Chain rule
    3. The attempt at a solution

    My answer:

    2(x^2+2x+5)*(2x+2)*2
     
  2. jcsd
  3. Feb 7, 2013 #2
    Why did you apply the chain rule again to (2x+2)? You only need to do it once.

    It should be:

    ##2(x^2 + 2x + 5)(2x + 2)##

    Think of it this way: ##f(x) = x^2## and ##g(x) = x^2 + 2x + 5##.

    Then, ##D(f \circ g)(x) = Df(g(x))D(g(x))##
     
    Last edited: Feb 7, 2013
  4. Feb 7, 2013 #3
    You could also just multiply it out and use the power rule.
     
  5. Feb 7, 2013 #4

    Mark44

    Staff: Mentor

    Torshi, your title is misleading. The derivative you show is not correct for online submission, AND it is not correct, as Karnage1993 points out.
     
  6. Feb 7, 2013 #5
    I didn't mean it to be misleading. My fault. The reason why I said that was because I was at my university math lab and even one of the math instructors said it was correct, but made a tad mistake until I mentioned it. I figured out the answer though.
     
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