Parallel & Perpendicular Lines
Parallel or Perpendicular?
Determining whether lines are parallel or perpendicular can be done by comparing the slopes of the lines. When given points on the line, find the slopes of each line using the slope formula. Then compare these slopes. When given the equations of the lines, rewrite each equation in slope-intercept form in order to find the slopes. Then compare these slopes.
Remember that parallel lines have the same slope, 
, but different y-intercepts. And perpendicular lines have slopes which are the opposite reciprocals of each other 
. In otherwords, the product of the slopes of perpendicular lines equals -1 or 
.