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Homework Help: Center and radius of a sphere

  1. Jan 20, 2007 #1
    1. The problem statement, all variables and given/known data

    The equation represents a sphere.


    Find its center, and radius

    2. Relevant equations

    3. The attempt at a solution
    i found the center by completing the square:

    16[(x-3)^2 +(y+1)^2 +(z+0)^2]=15

    the center is (3,-1,0)
    i thought the radius would be (15^.5)/4 but that was incorrect if someone could please help me thank you
  2. jcsd
  3. Jan 20, 2007 #2
    You forgot to multiply the added 1 and 9 on the right side by 16. Either multiply everything out on the left side and see what needs to be added to equalize the right side or try going back and dividing everything by 16 before completing the square.
    Last edited by a moderator: Jan 20, 2007
  4. Jan 20, 2007 #3
    ok i see what i did wrong. thank you very much
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