Simple Linear Algrebra find a point

  • Thread starter krisrai
  • Start date
  • #1
krisrai
15
0

Homework Statement


Given the two points P(-4,-5,0) and Q(5,5,-3) find the point R that is 1/4 of the way from Q to P.


Homework Equations



PQ = Point Q- Point P

The Attempt at a Solution


I got my direction vector as
PQ= [9,10,-3]

but i don't know how to find R

All i know is that the answer is supopsed to be:
R(2.75,2.5,-2.25)

Im wanted to add 1/4 of my direction vector PQ to my point q but this doesn't give me the right answer
 

Answers and Replies

  • #2
tmc
290
1
Your vector is from P to Q. You want a vector from Q to P (so, QP=[-9,-10,3]).
Then, R = Q + 1/4*QP.
 
  • #3
armis
103
0
You are on your way to the right answer!
When you calculate your direction vector [tex] \vec{PQ} [/tex] you actually get a vector which starts at point (0.0) and ends at the vector coordinates you get which in your case are (9,10,-3)
But your point Q is not (0,0), isn't it?
 

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