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Integration by parts help

  1. Jun 4, 2009 #1
    1. The problem statement, all variables and given/known data

    integral limit 1 to 5

    integral of sqrt x * lnx dx

    a = 1
    b= 5

    2. Relevant equations






    3. The attempt at a solution


    2
    x (-1 + 2 Log[x])
    ------------------
    8

    11.99604193 but its not right
     
  2. jcsd
  3. Jun 4, 2009 #2

    rock.freak667

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    Homework Helper

    Not sure how you reached that answer but did you use

    u=lnx and dv=x1/2 dx ?
     
  4. Jun 4, 2009 #3
    so is this right

    du = 1/x dx

    v = 3/2x^3/2

    and plug into the parts formula?
     
  5. Jun 4, 2009 #4

    rock.freak667

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    Homework Helper

    v=2/3 x3/2

    check that back.

    then yes put that into the formula.
     
  6. Jun 4, 2009 #5
    yes so i get this is this right after integrating

    2/3 x^3/2 ln x (between limits 1 to 5 ) - 4/9 x^3/2 (between limits 1 to 5) and

    i get 9.602
     
  7. Jun 4, 2009 #6
    Your calculus looks correct, but somehow you're not coming up with the right number. Re-check your computations and you should get approximately 7.47.
     
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