if the lines are paralell, the slopes are the same
if the lines aer perpendicular, the slopes multiply to get -1
if neither, then neither
for (x1,y1) and (x2,y2), the slope of line passing through them is (y2-y1)/(x2-x1)
line 1: (2,0) and (-2,2)
slope=(2-0)/(-2-2)=2/-4=-1/2
line 2: (1,-2) and (4,4)
slope=(4-(-2))/(4-1)=(4+2)/3=6/3=2
-1/2≠2 so not paralell
(-1/2)(2)=-1 so they are perpendicular
