Find the unit vector in the direction of vector PQ,
uuur
 where P and Q are the points
(1, 2, 3) and (4, 5, 6), respectively 9 For given vectors, 
ˆ
ˆ
ˆ
ˆ
ˆ
ˆ
2
2   and
a
i
j
k
b
i
j
k
=
−
+
= − +
−
r
r
, find the unit vector in the
direction of the vector a
b
+
r
r 10