Question

What is is the equation of the line perpendicular to y = 3x-7 that contains the point (6,8)?

A. 1/3x - 7
B. 1/3x + 6
C. -1/3x - 7
D. -1/3x + 10

Answer 1

The slope of the perpendicular line will be the negative reciprocal of 3, the slope of the given line.
  m = -1/(3) = -1/3

Only choices C and D have this slope. Only choice D goes through the given point. (-1/3)*6 +10 = -2 +10 = 8.

The appropriate selection is ...
  D. (-1/3)x + 10