Which of the following lines is perpendicular to the line 3x – 9y = 17?

Question

A.12x + 6y = 4

B. 9x – 3y = 11

C. 6x + 2y = 8

D. 3x – y = 5

Answer 1

Perpendicular lines have opposite, reciprocal slopes, like 2 and -1/2.

3x - 9y = 17

-9y = -3x + 17

y = (1/3)x - 17/9

A. 12x + 6y = 4

6y = -12x + 4

y = -2x + 2/3

-2 is not the opposite reciprocal of 1/3, so A is not your answer.