VITEEE 2012 Paper

Let z1,z2 and z3 be affixes of points A, B and C, respectively. Since, z1,z2 and z3 are in AP, therefore
2z1 = z1+3
⇒ z2 =

z1+z3

2

So, B is the mid-point of the line AC.
⇒ A, B and C are collinear.
∴ z1,z2 and z3 lie on a line.