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Math Help - Integration (substitution)

  1. #1
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    Integration (substitution)

    Hey guys first post here .

    I have an integration problem, and I thought I had it right, but I guess not lol. Can anyone tell me what I am doing wrong?

    integrate: (e^3x)/(e^3x+1)dx or e^3x * 1/e^3x+1*dx

    u = e^3x+1
    du = e^3x*dx

    = 1/u*du

    = ln|u|

    = ln|e^3x+1|

    Thanks for any tips/advice and your time
    Last edited by Ironmaiden22; August 31st 2009 at 08:58 PM.
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  2. #2
    Rhymes with Orange Chris L T521's Avatar
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    Quote Originally Posted by Ironmaiden22 View Post
    Hey guys first post here .

    I have an integration problem, and I thought I had it right, but I guess not lol. Can anyone tell me what I am doing wrong?

    integrate: (e^3x)/(e^3x+1)dx or e^3x * 1/e^3x+1*dx

    u = e^3x+1
    du = 3e^3x*dx

    = 1/u*du

    = ln|u|

    = ln|e^3x+1|

    Thanks for any tips/advice and your time
    You're missing something. After you make the substitution, the integral becomes {\color{red}\tfrac{1}{3}}\int\frac{\,du}{u}...
    Last edited by Chris L T521; September 1st 2009 at 06:53 AM.
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  3. #3
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    ahh lol

    thanks man.
    Last edited by Ironmaiden22; August 31st 2009 at 10:07 PM.
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