Line A contains the points (−1, 5) and (1, −3). Line B contains the points (2, 3) and (−2, 2). Are the lines perpendicular? Explain your reasoning.

Question

Line A contains the points (−1, 5) and (1, −3). Line B contains the points (2, 3) and (−2, 2). Are the lines perpendicular? Explain your reasoning. 

Answer 1

(-1,5), (1,-3)

have a line with slope -4

(5+3)/(-1-1) = 8/-2 = -4

(2,3) (-2,2)

have a line with slope =

(3-2)/(2+2) = 1/4

A and B are perpendicular

to be perpendicular the lines' slopes are negative inverses

1/4 is the negative inverse of -4

take 1/4 flip it upside down and change its sign, gives you -4/1 = -4