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Homework Help: Volume of Revolution

  1. Feb 4, 2007 #1
    1. The problem statement, all variables and given/known data
    "The region bounded by the given curves is rotated about the specified axis. Find the volume of the resulting solid by any method."

    y=5, y=x+4/x; about x=-1

    2. Relevant equations
    Upon plotting it I decided it would be best to use the shell method. I'm not sure how to express it in your fancy symbols but I included all of my work as an attachment.

    3. The attempt at a solution
    Please see attachment. The correct answer is actually 8pi(3-ln4). I have gone over it a few times and I don't see what I did wrong. Any advice whatsoever would be great, thanks.

    P.S. Sorry the image is grainy, I didn't know how to make it small enough to fit the guidelines and still be legible.

    Attached Files:

  2. jcsd
  3. Feb 4, 2007 #2
    Ah I just figured it out. I accidentally wrote 5-x+4/x, when i really meant 5-(x+4/x).

    Stupid parantheses!!!!
  4. Feb 5, 2007 #3


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    Science Advisor

    Perhaps it's not the parentheses that are stupid!:rolleyes:
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