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Math Help - perpetual integration

  1. #1
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    perpetual integration

    somebody please help me:
    I have to integrate the following:



    as you can see I have an answer - this is such a long problem - it's like an integration of an integration of an...
    and the final answer gives a math error in the calculator.

    I also get a value out of calculator of -7.169337845

    thank for any advice
    Attached Thumbnails Attached Thumbnails perpetual integration-q5a8-answer.gif  
    Last edited by stealthmaths; March 18th 2010 at 11:40 AM. Reason: ne winformation
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  2. #2
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    Quote Originally Posted by stealthmaths View Post
    somebody please help me:
    I have to integrate the following:



    as you can see I have an answer - this is such a long problem - it's like an integration of an integration of an...
    and the final answer gives a math error in the calculator.

    I also get a value out of calculator of -7.169337845

    thank for any advice
    go to the link ... scroll down to the tabular method of integration by parts.

    Integration by Parts
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  3. #3
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    yes i know integration by parts.
    I have done the integration but it is extremely long
    it just keeps going into more integration by parts.
    until i get the final values below.

    but i'm not sure this is correct as it such a long solution.
    i haven't put the workings here as i have an exam to revise for tomorrow and this also has to be handed in in the morning. it will take so long to input and i think it has gone wrong.
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  4. #4
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    Quote Originally Posted by stealthmaths View Post
    yes i know integration by parts.
    I have done the integration but it is extremely long
    it just keeps going into more integration by parts.
    until i get the final values below.

    but i'm not sure this is correct as it such a long solution.
    i haven't put the workings here as i have an exam to revise for tomorrow and this also has to be handed in in the morning. it will take so long to input and i think it has gone wrong.
    one more time ...
    look at the section in the link titled tabular method
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  5. #5
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    yes sorry skeeter. i was just looking at it.
    very nice
    i will try it now
    thanks
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  6. #6
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    ok. here it is. but I think I will loose marks for this method as we haven't been shown it yet.
    But I like it! I like it a lot

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  7. #7
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    sorry
    sleeping whilst typing
    could somebody check this for me please
    thank you

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  8. #8
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    Quote Originally Posted by stealthmaths View Post
    sorry
    sleeping whilst typing
    could somebody check this for me please
    thank you

    Wrong. I got a different solution:

    http://integrals.wolfram.com/index.jsp?expr=2x^3+e^-x&random=false

    You forgot the x in the third multiplication and forgot to do the last multiplication. You also got half of signs wrong .
    It's more like this.

    |-2e^{-x} x^3 - 6e^{-x} x^2 -12 e^{-x} x -12 e^{-x}|_{0}^{3}
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  9. #9
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    This is the solution worked out the integration by parts method. It is not checked yet though, so not sure if its right.

    Attached Thumbnails Attached Thumbnails perpetual integration-q5.1a8.gif  
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