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Homework Help: Point of intersection of 2 parametric lines

  1. Sep 3, 2008 #1
    Consider the two lines
    L1: x=-2t y=1+2t z=3t and
    L2: x=-9+5s y=36+2s z=1+5s
    Find the point of intersection of the two lines.

    My teacher said that I should use system of equations to solve for the point, but I am sort of confused on what to do because there are 2 variables. Is there something obvious that I am overlooking because this problem doesn't seem too hard. I tried making an equation containing t in terms of s and then plugging in the s for an x value, but I still get a wrong answer.
  2. jcsd
  3. Sep 3, 2008 #2


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    Set x,y and z in L1 equal to x,y and z in L2. That gives you three equations in two the two unknowns s and t. Pick any two of them and solve for s and t. Is that consistent with the third equation? They are consistent. If you are getting a wrong answer can you show us how you got s and t and what you got?
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