If 
ˆ
ˆ
ˆ
ˆ
ˆ
ˆ
ˆ
ˆ
ˆ
,  
2
3
and   
2
a
i
j
k
b
i
j
k
c
i
j
k
= +
+
=
−
+
= −
+
r
r
r
, find a unit vector parallel
to the vector 2
–  
3
a
b
r+c
r
r 8 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