You can
put this solution on YOUR website!You don't need to use the distance formula (in fact I don't think it will help at all). What you need to do is show that the slope of the line through (0,1) and (6,3) is equal to the slope of the line through (6,3) and (-3,0). If you do that, it will show you that these points lie on the same line ie they are collinear.