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!

Tough integral out of strategies

  1. Sep 11, 2008 #1
    1. The problem statement, all variables and given/known data

    ∫x2e-2|ax| dx

    3. The attempt at a solution

    tried to integrate by parts but I just ended up with a more difficult integral including an x3 times the e-2|ax|

    I've also tried substituting y=2ax

    to get 1/(2a)∫y2e-y dx

    but where do i go from there? and can I just ignor the absolute value?

    Can anybody recommend another strategy? How can I accommodate the absolute value?

    Thank you
    Last edited: Sep 11, 2008
  2. jcsd
  3. Sep 11, 2008 #2
    Well, yeah...intergrate by parts!!!! and try to reduce x^2!! that is write e^(whatever) as the u'...so that when you apply the formula, you actually differentiate x^2...thus making it 2x...then do it again...and make it 2...then you will have nothing more than an integral with e(whatever that was)...You were just applying the formula wrong...and probably writing x^2 as (1/3*x^3)' ...DONT DO THAT! =)
  4. Sep 11, 2008 #3
    OH YEAH! DONT IGNORE THE ABSOLUTE VALUE...cause e^(-x) is a lot different that e^(x)...do you have limits on that integral?
  5. Sep 11, 2008 #4


    User Avatar
    Homework Helper

    Just factor out a: [tex]|ax| = |a||x|[/tex]. Keep the absolute sign there. Integration by parts works fine. Just do it twice.
  6. Sep 11, 2008 #5
    Thank you!
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Discussions: Tough integral out of strategies
  1. Integration strategy? (Replies: 1)

  2. A tough integral (Replies: 1)

  3. Tough integral (Replies: 1)

  4. Tough integral (Replies: 2)

  5. Tough Integral (Replies: 3)