1. Algebra 4.2 Graphing Equations of Lines

2. Slope-Intercept Form y = mx + b slope y-intercept where the line crosses the y axis rise run

3. The y - intercept (b) is the point where the line crosses the y axis. For example: In the equation y = 2x – 5 Y - intercept The y-intercept is -5 So the line crosses the y-axis at the point (0, -5)

4. The slope (m) is a number that describes the whether the line goes uphill or downhill. Positive slope UPHILL line Negative slope DOWNHILL line For example, in the equation y = 2x - 5 Slope The slope is positive 2 The line is uphill

5. The slope (m) also describes the steepness of the line as the ratio RISE. RUN For example, in the equation y = 2x - 5 Slope The slope is 2 so the line RISES2 from point to point RUNS1

6. Slope and y - intercept Equation Slope rise run Uphill or downhill Y = 3x - 2 Y = - 1 x + 4 3 Y = 3 x + 6 4 Y = - 5 x – 3 2 3 3 3 4 -5 2 Uphill Downhill Uphill Downhill 3 1 3 3 4 -5 2 y - intercept - 2 4 6 -3

7. You have previously graphed using an X/Y Table.

8. x y y = 2x + 3 2 7 15 03 1. (2,7). (0,3). (1,5). (-1,1) x y This is the graph of the equation y = 2x + 3

9. Today you will learn an easy method of graphing that uses only the y-intercept (b) and the slope (m).

10. Graphing the y-intercept y = 2x + 3. (0,3) x y The y intercept of the line is 3. Plot the point (0,3) on the y axis.

11. Using the slope to find more points y = 2x + 3. (0,3). (1,5) x y The slope of the line is 2 or From the point (0,3) use the graph paper to: rise 2 (go up by 2) and run 1 (go right by 1). This takes you to the point (1,5) rise 2 run 1 Rise 2 Run 1

12. Using the slope to find more points. (0,3). (1,5) x y From the point (1,5) use the graph paper to: rise 2 (go up by 2) and run 1 (go right by 1). This takes you to the point (2,7) rise 2 run 1. (2,7) Rise 2 Run 1

13. . (0,3). (1,5) x y. (2,7) Connect the three points to graph the line y = 2x + 3

14. Graphing the Equation for a Line STEPS 1.Get the equation in Slope-Intercept Form y = mx + b Isolate the yslope y-intercept

15. Graphing the Equation for a Line STEPS 2.Plot the y-intercept 3.Use the slope to plot at least two more points (rise, run, plot…..repeat) 4.Connect the points as a line 5.Test a point

16. Now try graphing some equations of your own using a graphing website

17. http://www.webmath.com/gline.html

18. Homework Go srvhs.org and link to my website Find the link for the Algebra “Graphing Lines Using Slope- Intercept Form” Assignment Graph 30 lines. Print out your final graph. Keep a tally and have your parent sign off on the sheet that you graphed 30 lines using the animated software.