Question

Prove that the points A(1 , -1 ) B(5, 2) C(9, 5) are collinear.​

Answer 1

AB=
`\sqrt(5-1)^2 +(2+1)^2 = \sqrt16+9 =5`

BC=
`\sqrt(5-9)^2 + (2-5)^2 = \sqrt16+9=5`

AC =
`\sqrt(1-9)^2 + (-1-5)^2 = \sqrt64+36 = 10`

So, AC = AB + BC

A, B, C are collinear points

Explanation:

I hope this helps!