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Homework Help: Confused - simple differentiation with simplification

  1. Apr 11, 2012 #1
    1. The problem statement, all variables and given/known data
    differentiate the following
    y= x(x+2)(x+3)

    2. Relevant equations

    3. The attempt at a solution

    The answer I'm given is dy/dx = 2x+5
    Would this not be for (x+2)(x+3) = x2 +5x +6
    dy/dx = 2x +5 +0

    My problem is the x at the beginning of the brackets. Please help!
  2. jcsd
  3. Apr 11, 2012 #2
    Multiply the equation out and then differentiate, that answer given by the book doesn't seem right.
  4. Apr 11, 2012 #3


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    Homework Helper

    You're right. With the x at the beginning, the final answer is a quadratic expression.
  5. Apr 11, 2012 #4


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    Staff Emeritus
    Science Advisor
    Gold Member

    Er...I think I agree actually. Once you multiply through by x, you get x^3 + 5x^2 + 6x.

    The derivative of that is not what was given in the answer.
  6. Apr 11, 2012 #5
    cheers guys I'm going nuts the question states x(x+2)(x+3)
    with the answer of 2x+5
  7. Apr 11, 2012 #6
  8. Apr 11, 2012 #7
    thanks for the above link
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