How to tell if something is parallel or perpendicular from equations

Question

anonymous · Answer

y=4x-2 and y=-1/4x and y=-4x+1. How do I tell if this is parallel or perpendicular?

anonymous · Answer

if it is parallel, the slope will be the same.
if it is perpendicular, the slope will be the negative reciprocal.
y = 4x - 2 (slope is 4)
y = -1/4x (slope is -1/4) this is the negative reciprocal. When you " flip " the fraction and change the sign.
These two equations are perpendicular.

as far as y = -4x + 1.....it is not parallel or perpendicular to the other two equations.
If the slope would have been just 4x, it would have been parallel to y = 4x - 2.
if the slope would have been -1/4x, it would have been perpendicular to y = 4x - 2.

Do you understand ?