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Math Help - integration by parts

  1. #1
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    integration by parts

    Hello. As part of a question i have to integrate xe^(-x^2). I thought the easiest way to do this is by integration by parts however when i do it it seems to end up with horrible answers. I know this is quite simple but if anyone could help me here it would be good. thanks
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  2. #2
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    I did it using substitution
    firts, make a=-x^2
    now, da=-2x dx

    now the integral looks like:
    -(1/2) [Integral] e^a da

    and just integrate, with the answer being:
    -(1/2) e^a + C

    and substitute back

    -(1/2) e^(-x^2) + C


    I think that's about right.



    PS. [Integra] is the integral sign
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  3. #3
    Super Member wingless's Avatar
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    \int x.e^{-x^2}~dx

    Hint: Substitute u=-x^2.
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  4. #4
    Super Member wingless's Avatar
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    Quote Originally Posted by enmascarado View Post
    I did it using substitution
    firts, make a=-x^2
    now, da=-2x dx

    now the integral looks like:
    -(1/2) [Integral] e^a da

    and just integrate, with the answer being:
    -(1/2) e^a + C

    and substitute back

    -(1/2) e^(-x^2) + C


    I think that's about right.
    Yes, it's right
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