Help with finding variables in vectors?

Relative to an origin O, the position vectors of points A, B and C are given by

vec(OA) = (0, 2, -3)
vec(OB) = (2, 5, -2)
vec(OC) = (3, p, q)

In the case where angle ABC is a straight line, find the values of p and q.

1 Answer
Sep 21, 2017

p=13/2,q=-3/2

Explanation:

"since A, B and C all lie in a straight line"

"then they are "color(blue)"colinear"

rArrvec(BC)=kvec(AB)larr" k is a scalar"

vec(AB)=ulb-ula=((2),(5),(-2))-((0),(2),(-3))=((2),(3),(1))

vec(BC)=ulc-ulb=((3),(p),(q))-((2),(5),(-2))=((1),(p-5),(q+2))

"to find k we can only use the direction values of the"
"x-components"

"that is "2to1rArrk=1/2

rArrp-5=3/2rArrp=13/2

rArrq+2=1/2rArrq=-3/2