1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Integral error

  1. Feb 12, 2014 #1


    User Avatar
    Gold Member

    1. The problem statement, all variables and given/known data

    Evaluate: [tex]\int{xe^{ax}}dx[/tex]

    2. Relevant equations

    Integration by substitution

    3. The attempt at a solution

    I'm on a phone at the moment. My work: http://postimg.org/image/v4hdr5uqx/ [Broken]

    The correct answer was:
    Last edited by a moderator: May 6, 2017
  2. jcsd
  3. Feb 12, 2014 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    You should do this integral by parts. Some of your original substitutions don't look OK.
  4. Feb 12, 2014 #3


    User Avatar
    Gold Member

    http://postimg.org/image/ao3mi4ygz/ [Broken]

    I feel like I'm getting closer but I'm still making a dumb mistake. Is it with the derivatives?
    Last edited by a moderator: May 6, 2017
  5. Feb 12, 2014 #4


    User Avatar
    Homework Helper

    If [itex]dv = e^{ax} dx[/itex], then [itex]v = e^{ax}[/itex] is wrong. There are also multiple errors on the second line, but you need to fix what I said first.
  6. Feb 13, 2014 #5


    User Avatar
    Gold Member

    Got it. Thanks for pointing out my mistakes.
    [tex]\int{xe^{ax}}dx[/tex] [tex] u=x du=dx dv=e^{ax}dx v=\frac{e^{ax}}{a} [/tex]

    Power rule + derivative mistake
    Thanks for the help.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted

Similar Discussions: Integral error
  1. Integral Error (Replies: 4)

  2. Integration error (Replies: 1)

  3. Error-function integral (Replies: 11)

  4. Error in integration (Replies: 2)