Question

Determine if AB and CD are parallel,

perpendicular,
or neither.
A(8, -2), B(4, -1),
C( 3, 11), D(-2, -9)

Answer 1

Answer: AB and CD are perpendicular.

Explanation: You can calculate the slopes to see if they are parallel or perpendicular.

1. If they are parallel they must have the same slope.

Calculate slope of AB, call it
`$m_(1) = (-1-(-2))/(4-8)=(-1+2)/(-4) = (-1)/(4)$`

Slope of CD:
`$m_(2) = (-9-11)/(-2-3)=(-20)/(-5) = 4$.`

As we can see the lines are no parallel because their slopes are not the same.

2. If they are perpendicular then
`$m_(1)=(-1)/(m_(2))$` and they are!

Therefore, AB and CD are perpendicular.