This document discusses perpendicular and parallel lines. It provides examples of determining if lines are perpendicular or parallel based on their slope or equations. It also gives examples of finding the equation of a line parallel or perpendicular to a given line passing through a specific point. Key points covered include: - The product of the slopes of perpendicular lines is -1. - Lines are parallel if they have the same slope. - The equation of a parallel line can be found using the same slope and passing through a given point. - The equation of a perpendicular line can be found using the negative reciprocal slope and passing through a given point.