Is ab perpendicular to cd ? explain.

We know that
if two lines are perpendicular
then
the slopes 
m1*m2=-1

step 1
find the slope AB
A (0,2)
B (-3,-3)
m=(y2-y1)/(x2-x1)> m=(-3-2)/(-3-0)> m=-5/-3> m1=5/3

step 2
find the slope CD
C (-4,1)
D (0,-2)
m=(y2-y1)/(x2-x1)> m=(-2-1)/(0+4)> m=--3/4> m2=-3/4

step 3
multiply mi*m2
(5/3)*(-3/4)> -15/12
so
15/12 is not -1
therefore
 AB is not perpendicular to CD