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.

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

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