As Darrell K said, these are not collinear points. If they were then the slope between any
two points would be the same.
Slope between (p+1,p), (p, p+1) = slope between (p, p+1), (p-1,p-2)
(p+1-p)/[p-(p+1)] = [(p-2)-(p+1)]/(p-1-p)
1/-1 = -3/-1
-1 = 3
Since we do not arrive at a true statement, then the slopes are not equal;
thus, these points are not collinear.