Show that the following points are collinear:
A(8, 1), B(3, –4) and C(2, –5)
To show that the points are collinear, we show that the area of triangle is equilateral = 0
Δ = 0
Δ = 1/2{x1(y2−y3) + x2(y3−y1) + x3(y1−y2)}
⇒ 1/2{8(–4 + 5) + 3 (–5–1) + 2 (1 + 4)}
⇒ 1/2{8–18 + 10}
= 0
Hence collinear.