Question

Find the value of k for which points P(k, −1), Q(2, 1) and R(4, 5) are collinear.

Answer 1

Given, points P(k, −1), Q(2, 1) and R(4, 5) are collinear.

∴ Slope of PQ = Slope of QR

∴ `(1 - (-1))/(2 - "k") = (5 - 1)/(4 - 2)`

∴ `2/(2 - "k") = 4/2`

∴ 4 = 4 (2 − k)

∴ 1 = 2 − k

∴ k = 2 − 1 = 1