Explore the Lesson

A. Slope and Parallel Lines

Key Lesson Marker


In the Warm Up, you may have noticed that lines with the same slope are parallel.

Parallel Lines
lines that are parallel maintain a constant separation; parallel lines do not intersect



The slope of a line gives it 'direction', so it makes sense that lines with the same slope point in the same direction.

The slopes of vertical lines are not defined, so they are a special case of parallel lines. Vertical lines are parallel to each other.