How to determine if 3 points are collinear?

If the points are on the same line they are co linear. when working with coordinates if the all have the same y as in (x,y) they are on the same line for example, (4,5) (2,5) (9,6) are collinear

You need to include the original coordinates of the triangle to answer this. and how much does it translate (move left right up down)