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Math Help - Integration help

  1. #1
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    Integration help

    I wan't too sure where to put this. It is Calculus, but not University level. Any how,

    I need to integrate:

    1/(3x+7)

    Now I'd be fine with it if the power wasn't -1 seeing as I get 0 on the bottom. I think it has to something do with lnx.

    Thanks.
    Last edited by StephenPoco; March 8th 2010 at 07:00 AM.
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  2. #2
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    Quote Originally Posted by StephenPoco View Post
    I wan't too sure where to put this. It is Calculus, but not University level. Any how,

    I need to integrate:

    1/(3x+7)

    Now I'd be fine with it if the power wasn't -1 seeing as I get 0 on the bottom.

    Thanks.
    That's why it doesn't work..

    \int{\frac{1}{x}}dx=ln|x|

    \int{\frac{1}{u}}du=ln|u|

    Hence u=3x+7\ \Rightarrow\ \frac{du}{dx}=3\ \Rightarrow\ du=3dx\ \Rightarrow\ dx=\frac{du}{3}

    The integral is now solved using

    \frac{1}{3}\int{\frac{1}{u}}du=\frac{1}{3}ln|u|=\f  rac{1}{3}ln|3x+7|
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