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May have copied wrong

  1. May 10, 2007 #1
    I'm trying to integrate the following: int (x^3 + 4x)/sqrt(x^2-4) dx

    I let u= x^2-4
    so du/2 = xdx

    granted, the above also gives me x^2=u+4 so, this gives me:

    1/2 int u+8 u^-1/2 du

    but the professor has:

    1/2 int [u^1/2+8 u^-1/2] du

    Did I miss the first u^1/2 somewhere??? where did it come from?
  2. jcsd
  3. May 10, 2007 #2
    Never mind... I found my answer:

    (u+8)u^-1/2= u^1/2 + 8u^-1/2

    Sorry about that! I forgot the parenthesis!
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