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Geometry Scalar Equation Help

  1. Apr 4, 2006 #1
    The question is,

    Find a scalar equation that passes through the points (3,2,3), (-4,1,2) and (-1,3,2).

    What I did was put that into the vector equation form, using (3,2,3) as a position vector, resulting in:

    r=(3,2,3) +t(-7,-1,-1) + s(-5,2,0)

    Then I found the cross product of the directional vectors and went from there, but my final answer was different then the one in the text book. Can someone tell me what I did wrong please?
  2. jcsd
  3. Apr 4, 2006 #2


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    Science Advisor

    s should be multiplied by (-3, 2, 0). Looks like you added instead of subtracted.

    The better way to do this problem is to solve the system of equations, with matrix algebra if you have it.
  4. Apr 4, 2006 #3


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    Science Advisor

    I have no idea what it means for an "equation" to pass through three points. A line or a plane can pass through points but an equation is not a geometric object and has nothing to do with "points".
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