a line perpendicular to another will have the opposite sign and be flipped
ex: slope is 4/5 the other lines slope will be -5/4
(-2,-1) (2,-3)
slope formula
y2-y1/x2-x1
-3-(-1)
____
2-(-2)
-3+1
___
2+2
-2
___
0
the slope of the perpendicular line is 0/-2 which is just 0
