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calculus - please help!

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Find the volume of the solid obtained by rotating the region bounded by the given curves about the specified axis.
y=2+1/x^4,y=2,x=4,x=9;
about the x-axis.

  • calculus - please help! -

    Int(2 + 1/x^4 - 2 dx)[4,9]
    = -1/3 x^-3 [4,9]
    = -1/3(1/729 - 1/64)
    = 665/139968
    = 0.00475

  • calculus - oops -

    Sorry - we wanted a solid

    v = Int(pi (R^2-r^2) dx)
    where R = y = 2+x^-4
    and r = 2

    pi*Int(2+x^-4)^2 - 4 dx [4,9]
    pi*Int(4+4x^-4 + x^-8 - 4 dx)[4,9]
    pi*Int(4x^-4 + x^-8 dx) [4,9]
    -pi*(28/x^3 + 1/7x^7)
    = 0.0597

  • calculus - please help! -

    thank you soo much! :D

  • calculus - please help! -

    Hmm. I didn't see where you specified an axis. I rotated around the x-axis.

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