How do i determine three points are collinear? using the vector equation of a line?
a (3, -8) b(5/2, 6) and c(-1/2, 90)

A collinear points if they line on a single straight line in the plane. A line on which point lie, specially if it is related to a geometric figure such as triangle, is sometimes called an axis. In determining that the said points are collinear, you have to plot the points. I hope you are satisfied with my answer and feel free to ask for more