1. Chapter 4 – Graphing Linear Equations 4.4 – The Slope of a Line

2. Today we will be: –Finding the slope of a line using two of its points –Interpret slope as a rate of change in real- life situations

3. 4.4 – The Slope of a Line Slope – (m) – The number of units a nonvertical line rises or falls over the number of units the line changes from left to right. Two points on the line is all that is needed to find slope. SLOPE = rise run

4. 4.4 – The Slope of a Line

5. FINDING THE SLOPE OF A LINE –The slope m of a nonvertical line passing through the points (x 1, y 1 ) and (x 2, y 2 ) is: m = rise = change in y = y 2 – y 1 run change in x x 2 – x 1 Read x 1 as “x sub 1.” Think “x – coordinate of the first point.” Read y 2 as “y sub 2.” Think “y – coordinate of the second point.”

6. 4.4 – The Slope of a Line When finding slope, the order of subtraction IS important. You must use the same order for subtracting in the numerator and the denominator.

7. 4.4 – The Slope of a Line Example 1 –Find the slope of the line passing through (-3, 0) and (-1, 6).

8. 4.4 – The Slope of a Line Example 2 –Find the slope of the line passing through (-1, -3) and (5, -3).

9. 4.4 – The Slope of a Line Example 3 –Find the slope of the line passing through (-2, 1) and (1, -3).

10. 4.4 – The Slope of a Line Example 4 –Find the slope of the line passing through (0, -1) and (0, 4).

11. 4.4 – The Slope of a Line CLASSIFICATION OF LINES BY SLOPE –A line with positive slope rises from left to right

12. 4.4 – The Slope of a Line CLASSIFICATION OF LINES BY SLOPE –A line with negative slope falls from left to right

13. 4.4 – The Slope of a Line CLASSIFICATION OF LINES BY SLOPE –A line with zero slope is horizontal

14. 4.4 – The Slope of a Line CLASSIFICATION OF LINES BY SLOPE –A line with undefined slope is vertical

15. 4.4 – The Slope of a Line RATE OF CHANGE – compares two different quantities that are changing. –Same as slope, but compares real-life quantities.

16. 4.4 – The Slope of a Line Example 5 –You are traveling by car and leave your home at 8:00 a.m. By 8:45 a.m., you are 36 miles from home. Find the average speed in miles per hour.

17. 4.4 – The Slope of a Line HOMEWORK Page 230 #12 – 36 even