1. Parallel/ Perpendicular Lines Section 2.4

2. If a line is written in “y=mx+b” form, then the slope of the line is the “m” value. If lines have the same slope, then they are parallel. If a line is written in “y=mx+b” form, then the slope of the line is the “m” value. If lines have the same slope, then they are parallel.

3. Parallel lines never intersect.

4. Example Are the lines parallel? y = 2x + 6y = 2x - 3 Graph the lines to see the relationship. Are the lines parallel? y = 2x + 6y = 2x - 3 Graph the lines to see the relationship.

5. Example Are the lines parallel? -2x - y = -5 y = 2x + 6 Are the lines parallel? -2x - y = -5 y = 2x + 6

6. Perpendicular Lines Perpendicular lines are lines that intersect at a 90 degree angle (a right angle).

7. Two lines are perpendicular if the slopes of the lines are opposite reciprocals. Opposite: signs are different, one positive, one negative Reciprocals: switch the numerator and the denominator. Two lines are perpendicular if the slopes of the lines are opposite reciprocals. Opposite: signs are different, one positive, one negative Reciprocals: switch the numerator and the denominator.

8. Example Are the lines parallel, perpendicular, or neither? 6y = -2x + 12 36x - 12y = 24 Are the lines parallel, perpendicular, or neither? 6y = -2x + 12 36x - 12y = 24

9. Example Are the lines parallel, perpendicular, or neither? -x + y = 3y = x - 8 Graph the lines to see the relationship. Are the lines parallel, perpendicular, or neither? -x + y = 3y = x - 8 Graph the lines to see the relationship.

10. Remember Same Slope = parallel Opposite Reciprocals = perpendicular Same Slope = parallel Opposite Reciprocals = perpendicular