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Integration Help

  1. Nov 8, 2007 #1
    I can't seem to figure this integral out
    [tex]\int[/tex]x^(1/2)*e^(-x) dx
    from -[tex]\infty[/tex] to [tex]\infty[/tex]

    I have tried integrating by parts, but that didn't seem to do any good. Does anyone know a good way to start this problem?
     
  2. jcsd
  3. Nov 8, 2007 #2

    dextercioby

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    Y not make [tex] x=t^2 [/tex] ?
     
  4. Nov 9, 2007 #3
    Are we restricted to the reals? If so, then the limits of integration are not in the domain.
     
  5. Nov 9, 2007 #4

    D H

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    Substituting x=t2 does not yield a Gaussian. As sennyk noted, the integration limits cannot be -infinity to infinity.
     
  6. Nov 9, 2007 #5
    break the integral into two parts one from -inf to 0 and then 0 to inf...if any of those two intregrals diverge then the whole thing diverges
     
  7. Nov 9, 2007 #6
    The problem is more that the function isn't even defined on one of those intervals.
     
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