Question

Consider the line y = 2x–4.

What is the slope of a line parallel to this line?
What is the slope of a line perpendicular to this line?

Answer 1

the slope of the parallel line is 2x

the slope of line perpendicular is -1/2

Explanation:

Answer 2

Parallel slope = 2

This is because the original line has slope 2. Parallel lines have equal slopes.

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Perpendicular slope = -1/2

The original slope 2 or 2/1 turns into -1/2 after flipping the fraction and the sign. Note the original slope and perpendicular slope multiply to -1. This is true for any pair of perpendicular lines where neither line is vertical.