Question

Determine whether AB and CD are parallel, perpendicular, or neither. A(-3, 2), B(5, 1), C(2, 7), D(1, -1)

Answer 1

perpendicular

Explanation:

We'll find the slope of both lines and see what it tells us.

If the slopes are the same, the lines are parallel. If the slopes are opposite sign and flipped (negative reciprocals) then they are perpendicular.

The slope is y-Y on top of a fraction and x-X on the bottom.

Slope of AB:

m = 2-1 / -3 -5

= 1/-8 = -1/8

Slope of CD:

m = 7- -1 / 2-1

= 8/1 = 8

Since the slopes are -1/8 and 8, the lines are perpendicular, because they are opposite sign and flipped (negative reciprocals)