(a) Let A(2, 5), B(4, 6) and C(8, 8) be the given points

Area of ΔABC

Since, area of ΔABC=0

Therefore, (2,5) , (4,6) and (8,8) are collinear.

(b) Let A(1, -1), B(2, 1) and C(4, 5) be the given points

Area of ΔABC

Since, area of ΔABC=0

Therefore, The points (1, -1), (2, 1) and (4, 5) are collinear.