Show that the points A(1, – 2, – 8), B(5, 0, –2) and C(11, 3, 7) are collinear, and
find the ratio in which B divides AC 9 Find the position vector of a point R which divides the line joining two points
P and Q whose position vectors are (2
) and ( – 3 )
a
b
a
b
+
r
r
r
r
 externally in the ratio
1 : 2 Also, show that P is the mid point of the line segment RQ