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Homework Help: Revolving regions

  1. Mar 3, 2014 #1
    1. The problem statement, all variables and given/known data

    Find volume of the solid generated by revolving the region bounded by x = y^2, x=4
    about the line x = 5

    2. Relevant equations

    the washer method from c to d ∏∫ R(y)2 - r(y)2

    3. The attempt at a solution

    I set r(y) = 1 and R(y)= y^2

    and got the integral from 0 to 2 of ∏∫(y^2)^2-(1)^2

    I got an answer of 16.96 but i know this is wrong because the back of the book gives a different answer. Please tell me where I went wrong.
    Last edited: Mar 3, 2014
  2. jcsd
  3. Mar 3, 2014 #2


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    Staff Emeritus
    Science Advisor
    Homework Helper
    Gold Member

    Think about what the washer method involves -- why it's called the "washer" method.

    What do r(y) and R(y) represent?
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