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Homework Help: Volume of revolution problem

  1. Feb 15, 2006 #1


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    Find the volume created by revolving:
    [tex] y=x^2 +x - 2 [/tex]

    and y=0 about the x axis.

    [tex] y=x^2 +x - 2 [/tex] intersects the x axis at -1 and 1 so those are the bounds of integration.

    the radius of the figure = -([tex] y=x^2 +x - 2 [/tex])


    V = [tex] - \pi \int_{-1}^1 (x^2 + x - 2)^2 dx [/tex]

    After integrating that I get 18[tex]\pi[/tex]/5. The actual answer is 81[tex]\pi[/tex]/10. What I want to know is if i set the integral up right. If I did then this is only a stupid integration mistake. If not then I hope someone finds my mistake. Thanks for the help.
  2. jcsd
  3. Feb 16, 2006 #2


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    You may want to check that again :smile:
    Fix this, and you'll find the given answer.
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