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Homework Help: Evaluate a fraction in a definite integral?

  1. Sep 26, 2011 #1
    I don't understand how to evaluate a fraction in a definite integral, could anyone please explain this problem to me?

    int. between 3 (lower integral) and 4 (upper integral) of 3x^2+2/x^2

    I thought of using the substitution law, and got as far as 1/6 u * du/x ...I don't quite know how to proceed...

    Your help is greatly appreciated!
  2. jcsd
  3. Sep 26, 2011 #2


    Staff: Mentor

    The most obvious approach is to divide 3x2 + 2 by x2. I'm assuming that you meant (3x2 + 2)/x2. A literal interpretation of what you wrote would be 3x2 + (2/x2). You don't need to use substitution.

    BTW, there is no "substitution law." It's just a technique for evaluating integrals.
  4. Sep 28, 2011 #3
    thank you!!
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