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Vector equation problem help

  1. Jun 13, 2007 #1
    http://img404.imageshack.us/img404/5186/vectornw4.jpg

    'Write Down the vector AM and hence the coords of the point N which divides AM so that the ratio AN:NM = 2:1.'

    I know that ON = OA + AN

    And that the vecor equation is

    r = (0,0,6) + x(0,-4,-6)

    But the answer is 9/13 for x, which i dont understand. I thought it would be 2/3 or 2/3 of the length AM. Im really stuck.

    Thanks
     
  2. jcsd
  3. Jun 13, 2007 #2

    Dick

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    Just take (r-A)^2=2^2*(r-M)^2 and solve for x. Or just notice x=0 gives A and x=1 gives M so the x that splits it 2:1 must be 2/3.
     
    Last edited: Jun 13, 2007
  4. Jun 13, 2007 #3
    so ur saying x = 2/3?

    thats what i said, but the answer says its 9/13 which i dont understand.
     
  5. Jun 13, 2007 #4

    Dick

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    If I'm understanding the question, yes, I say x=2/3.
     
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