How do you know if two line segments are perpendicular A. Their slopes are equal
B. The slope of one is the negative of the slope of the other
C. Their slopes are negative reciprocals
D. Their slopes are reciprocals

C. Their slopes are negative reciprocals

Step-by-step explanation:

The slopes of two perpendicular lines are negative reciprocals of each other.

answer:      

step-by-step explanation:

x = -3

y = -18

step-by-step explanation:

to solve by substitution, substitute one variable and solve for the other. then substitute again to find the remaining variable.

x-1/3(3x-9) = -3 since y=3x-9 substittute y.

x-1/3(3x-9)=-3

x + x +3 = -3

2x+3=-3

2x+3-3= -3-3

2x=-6

x=-3

substitute again into y=3x-9

y=3(-3)-9

y=-9-9

y=-18