Question

Show that points P (–2, 3, 5), Q (1, 2, 3) and R (7, 0, –1) are collinear.

Answer 1

For collinearity:

`Δ = |(-2, 3, 5),(1, 2, 3),(7, 0, -1)|` should be zero.

`Δ = |(-2, 3, 5),(1, 2, 3),(7, 0, -1)|`

= –2(–2 – 0) – 3(–1 – 21) + 5(0 – 14)

= 4 + 66 – 70

= 0

Hence, given points P, Q and R are collinear.