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Integration and taylor expansion

  1. May 16, 2008 #1
    can anybody help me with this integration?

    Integral of e to the -2x times x squared dx

    it expands to 1/4, but I'm not sure how to start.
     
  2. jcsd
  3. May 16, 2008 #2

    Hootenanny

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    Hey casanova, welcome to PF!

    You don't really need a Taylor expansion here, how about trying a substitution?
     
  4. May 16, 2008 #3
    I have tried substitution

    I've already tried substitution.

    argh!

    i've tried u = e ^ -2x

    I've also tried u = x squared.

    it doesn't work!!!!

    HELP!
     
  5. May 16, 2008 #4
    Integrate by parts and it works.
     
  6. May 16, 2008 #5
    start me off

    with what do I start?
     
  7. May 16, 2008 #6

    rock.freak667

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    you start by integrating

    [tex]\int xe^{-2x}dx[/tex]

    by parts.
     
  8. May 16, 2008 #7
    You integrate by parts. Start with x squared. You get

    u = x^2
    du = 2x dx

    dv = e^-2x dx
    v = -1/2 e^-2x

    Give it a shot from there.
     
  9. May 17, 2008 #8
    thanks

    i get it now....just needed a refresher....thanks a lot!
     
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