Question

The points with position vectors 60i + 3j, 40i – 8j, ai – 52j are collinear if 

(a) a = – 40

(b) a = 40

(c) a = 20

(d) None.

Answer 1

Answer is (a) - 40

Explanation:

Let OP = p = 60i + 3j,

OQ = q = 40i – 8j

and OR = r = ai – 52j

Since the points are collinear, so

= –100 – a + 60 

a = –40.