Question

Which pair of equations are perpendicular lines? A. 5x + 2y = 9 and y = –5/2x+27/2 B. x – 3y = 11 and y = –3x + 23 C. 4x + 2y = 6 and y = –2x + 18 D. x – 3y = 5 and y = 3x – 1

Answer 1

Answer: B x - 3y = 11 and y = -3x + 23
Explanation:
Two lines that are perpendicular have slopes that are negative reciprocals, meaning if there are lines that have slope of 2 or 2/3 or -5, lines that are perpendicular have slopes of -1/2, -3/2, 1/5 respectively.

For this question, you must make each equation in terms of y (isolate y)

A: you get -5/2x -(9/2) = y and y = -5/2x + 27/2. Here, -5/2 = -5/2 so this can’t be it. We’re looking for negative reciprocals

B: you get y = 1/3x - 11/3 = y and y = -3x + 23.
1/3 and -3 are negative reciprocals of one another so this is your answer.