If two lines are perpendicular, which statement must be true?

a. their slops are reciprocals
b. their slopes are opposite
c. their slopes are the same
d. their slopes are negative reciprocals

If two lines on a graph are perpendicular, then
their slopes are negative reciprocals.

Examples:

-- slope of one line = 2 . . . . . slope of a perpendicular line = -1/2 .

-- slope of one line = -3/5. . . . slope of a perpendicular line =  5/3 .

-- slope of one line = 100 . . . . slope of a perpendicular line = -0.01 .