Prove that the points : `(x_1,y_1),(x_2,y_2),(x_3,y_3)`
are collinear if `[[x_1,y_1,1],[x_2,y_2,1],[x_3,y_3,1]]`=0

Explanation

From geometry, we know that, if the points A,B,C, are collinear, then the area of the traingle ABC with vertices `(x_1,y_1),(x_2,y_2)` and `(x_3,y_3)` is zero .
`[[x_1,y_1,1],[x_2,y_2,1],[x_3,y_3,1]]`=0