Question

Points F(3, 3), K(6, 5), J(8, 2) and L(5, 0) lie in a coordinate plane. Which lines are perpendicular?

Answer 1

To determine if a line is perpendicular to another, you must first determine the slope...
m = y1-y2/x1-x2
m of FK = 3-5/3-6 = -2/-3 = 2/3
m of FJ = 3-2/3-8 = 1/-5
m of FL = 3-0/3-5 = 3/-2
m of KJ = 5-2/6-8 = 3/-2
m of KL = 5-0/6-5 = 5
m of JL = 2-0/ 8-5 = 2/3

In order for two lines to be perpendicular, their slopes must be opposite reciprocals...
FK is perpendicular to FL
FK is perpendicular to KJ
JL is perpendicular to FL
JL is perpendicular to KJ
FJ is perpendicular to KL