Perpendicular lines are two lines that intersect and create 90 degree angles. ( right angles )
The slopes of perpendicular lines are negative reciprocals.
For example the negative reciprocal of 1 /2 = - 2/1
If the slope of line m is m=-4/2 then the perpendicular lines slope equals m = 2/4
Slope of a Line
Parallel lines are two lines in a plane that never intersect.
Parallel lines have the same slope.
Example Question 1 One line passes through the points (-2,-1) and (1, 2); another through the points ( 1,2 ) and (3,4) are they parallel, perpendicular, or neither?
Step 1. Find the slope of each line using the slope formula:
Step 2. Because the slope of each line is equal the lines are parallel.
Video Answer to Example Question 1