Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

I 1st year linear algebra question

  1. Jan 19, 2017 #1
    given P(-1,1,2), Q(-3,0,4), R(3,2,1), find an equation of the line through P that is parallel to the line through Q and R.

    All the words after the given three points really confuse me and I just need some help on where to start to tackle this problem.

    Thanks
     
  2. jcsd
  3. Feb 19, 2018 #2

    Ackbach

    User Avatar
    Gold Member

    Geometrically, you need to find a line going through P. But not just any line will do - it's gotta be parallel to another line. Which line does it need to be parallel to? The one going through Q and R. So, Step One would be to find the line going through Q and R.
     
    Last edited by a moderator: Feb 21, 2018
  4. Feb 21, 2018 #3

    mathwonk

    User Avatar
    Science Advisor
    Homework Helper

    since 2 days have passed, maybe more detailed help is warranted. basic facts: point - point = vector parallel to the line through the two points. point + vector = another point on the line through the first point and having the given direction vector.

    In general you can subtract 2 points and get a direction vector; and you can add a vector to a point to get another point on the line through the given point and parallel to the given vector.


    oops a year has passed!
     
    Last edited: Feb 21, 2018
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted