Determine if the points (1, 5), (2, 3) and (– 2, – 11) are collinear

Assume points (1, 5), (2, 3), and ( - 2, - 11) representing the vertices A, B, and C of the given triangle respectively.

Let A (1, 5), B (2, 3) and C (-2, -11)

Now,

AB = [(1 – 2)² + (5 – 3)²]^1/2

BC = [(2 + 2)² + (3 + 11)²]^1/2

CA = [(1+ 2)² + (5+ 11)²]^1/2

Since, AB + BC ≠ CA

Therefore, given points are not collinear