Results 1 to 4 of 4

Math Help - Integrate xe^x dx

  1. #1
    Junior Member
    Joined
    Sep 2009
    Posts
    29

    Integrate xe^x dx

    it is actually integrate from 0 to -infin, but I understand that part. When I see xe^x I integrate it and get (1/2x^2)(e^x). My solutions manuel says it is (x-1)(e^x). I don't get the same answer when using my work, what am I doing wrong?
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Super Member Matt Westwood's Avatar
    Joined
    Jul 2008
    From
    Reading, UK
    Posts
    806
    Thanks
    27
    Integrate by parts: \int u dv = uv - \int v du.

    Here you set u = x, dv = e^x and so uv = x e^x and \int v du = \int e^x = e^x.

    Hence, as they say, the result.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Junior Member
    Joined
    Sep 2009
    Posts
    29
    So how does (xe^x)-(e^x) become (x-1)e^x? I'm sure I'm missing some simple rule here...
    Last edited by Jameson; September 3rd 2009 at 02:10 PM.
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Member
    Joined
    Aug 2009
    Posts
    94
    Yes:

    (xe^x)-(e^x)

    = xe^x - e^x

    = e^x(x - 1)

    = (x - 1)e^x
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Integrate 3 e^x
    Posted in the Calculus Forum
    Replies: 4
    Last Post: June 9th 2010, 01:16 PM
  2. how to integrate this ??
    Posted in the Calculus Forum
    Replies: 8
    Last Post: August 9th 2009, 08:14 PM
  3. Integrate
    Posted in the Calculus Forum
    Replies: 7
    Last Post: April 28th 2009, 07:54 PM
  4. How to integrate x^x?
    Posted in the Calculus Forum
    Replies: 5
    Last Post: April 25th 2009, 07:51 PM
  5. Integrate
    Posted in the Calculus Forum
    Replies: 8
    Last Post: April 15th 2009, 03:50 PM

Search Tags


/mathhelpforum @mathhelpforum