Reminder: parallel lines, by definition never intersect (think train tracks). Perpendicular lines do intersect, but they must intersect at right angles (90 degrees).

When we consider the equation of lines, there are some standard properties related to the slope of parallel or perpendicular lines:

Parallel Lines:The slope of parallel lines are exactly equal: \(m_1 = m_2\) where \(m_1\) and \(m_2\) are the slopes of the parallel lines.

Perpendicular Lines:The slope of perpendicular lines are opposite reciprocals: \(m_1=-\frac{{1}}{m_2}\) where \(m_1\) and \(m_2\) are the slopes of the perpendicular lines