1. § 7.3 Slope of a Line

2. Angel, Elementary Algebra, 7ed 2 Slope The slope of a line is the ratio of the vertical change between any two selected points on the line. Consider the points (3, 6) and (1,2).

3. Angel, Elementary Algebra, 7ed 3 Slope (3, 6) and (1,2) This means the graph is moving up 4 and to the right 2. Horizontal Change Vertical Change

4. Angel, Elementary Algebra, 7ed 4 Slope Horizontal Change Vertical Change m = 2 Simplifying,, so m = 2

5. Angel, Elementary Algebra, 7ed 5 Positive & Negative Slopes x y x y Positive SlopeNegative Slope Line rises from left to rightLine falls from left to right

6. Angel, Elementary Algebra, 7ed 6 Horizontal Lines Every horizontal like has a slope of 0. x = 2

7. Angel, Elementary Algebra, 7ed 7 Vertical Lines The slope of any vertical line is undefined. y = -4

8. Angel, Elementary Algebra, 7ed 8 Parallel Lines Two non-vertical lines with the same slope and different y-intercepts are parallel. Any two vertical lines are parallel to each other. m 1 = m 2

9. Angel, Elementary Algebra, 7ed 9 Perpendicular Lines Two lines whose slopes are negative reciprocals of each other are perpendicular lines. Any vertical line is perpendicular to any horizontal line. m 1 = m2m2