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Homework Help: Revolution using disk method

  1. Oct 26, 2007 #1
    1. The problem statement, all variables and given/known data

    Compute the volume of the solid formed in the first quadrant by y=x^4 and y=125x
    when rotated around the x axis.

    2. Relevant equations

    the integral for a disk is solved by taking the integral from a to b of pi R^2

    3. The attempt at a solution

    I found the integral's limits to be from 0 to 5. My problem is figuring out what to actually integrate. I have tried integrating both (x^4 - 125x)^2 and (125x - x^4)^2 with both yielding the same wrong answer. I then tried doing the integral for (125x)^2 from 0 to 5 and found that to be wrong also.
  2. jcsd
  3. Oct 26, 2007 #2
    I do not think this can be solved by "disks"....try washer method

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