Question

Determine which of the following equations are perpendicular to each other. I. y=-3x+2

II. -3x+2y=1
III. x+3y=1
IV. y+1/3x+9
A. I and III
B. I and IV
C. II and IV
D. None of these equations are perpendicular.

Answer 1

Write each equation in y = mx + b form so that you can compare the slopes.
Perpendicular slopes are opposite reciprocals.
For example: 2/3 and - 3/2; 4/5 and -5/4; 1/2 and -2

I. y = -3x + 2 m = -3
II. y = 3/2 x + 1/2 m = 3/2
III. y = - 1/3x + 1/3 m = -1/3
IV. y = 1/3x + 9 m = 1/3 (I assuming this one had a typo in it since there is no equal sign.)
LETTER B is the answer I & IV