In other words, the slopes of parallel lines are equal. Note that two lines are parallel if their slopes are equal and they have different y-intercepts. In other words, perpendicular slopes are negative reciprocals of each other.

Can two parallel lines have negative slopes?

Theorem 103: If two nonvertical lines are parallel, then they have the same slope. ... If two lines are perpendicular and neither one is vertical, then one of the lines has a positive slope, and the other has a negative slope. Also, the absolute values of their slopes are reciprocals.

Can lines have negative slopes?

Definition of Negative Slope Lines

A line with a negative slope is a line that is trending downward from left to right. In other words, the line's rise to run ratio is a negative value.