1. Graphing Lines Using Slope Intercept Form Algebra 1 Glencoe McGraw-HillLinda Stamper

2. In the previous unit, you graphed an equation using a table of values and plotting points to make a line. Today you will learn another method to graph an equation. This method uses the slope-intercept form. The linear equation y=mx+b is written in slope-intercept form where m is the slope and b is the y-intercept. slope y-intercept

3. Recall that the slope of a line can be calculated using y 2 – y 1 x 2 – x 1 Slope can also be counted using a graph by doing rise run The y-intercept of a line is where the line intersects the y-axis

4. Slope = -1/4 y-int = -1 Equation: y = (-1/4)x + -1 Slope = 4/3 y-int = 3 Equation: y = (4/3)x + 3 Slope = 0 y-int = 2 Equation: y = (0)x + 2 y = 2

5. Now let’s work BACKWARDS!! Instead of finding information from a graph – let’s use information to make a graph!!

6. Graph the equation y = –6x + 3. x y 1. Plot the y-intercept. 2. Use slope to locate second point. 3. Draw a line through the two points. How do you check if you have the correct graph? Using the coordinate of each point, substitute into the original equation. Does it produce true statements?

7. Graph the equation y = –6x + 3. x y Using the coordinate of each point, substitute into the original equation. Does it produce true statements? y = –6x + 3 (, ) coordinate for y-intercept 3 0 3 = –6(0) + 3 3 = 0 + 3 3 = 3 y = –6x + 3 (, ) coordinate for other points -3 1 -3 = –6(1) + 3 -3 = -6 + 3 -3 = -3

8. Example 1 Graph the equation y = –3x + 2. Example 2 Graph the equation y = 4x – 5. Example 3 Graph the equation How do you know by looking at these equations, that they will NOT graph as horizontal or vertical lines? Example 4 Graph the equation

9. Ex 1 y = –3x + 2. x Ex 2 y = 4x – 5. x Ex 3 x y Ex 4 x

10. Write the equation in slope-intercept form. Then graph. The equation. Rewrite in slope-intercept form (solve for y). slope is 2 y-intercept is 3 1 Graph. x y Using the coordinate of each point, substitute into the original equation. Does it produce true statements? How do you check if you have the correct graph?

11. Write the equation in slope-intercept form. Then graph. Example 5 Example 6

12. slope is 5 y-int. is –3 x y Example 5 y-intercept is 2 Example 6 x y Remember the negative can go in the numerator or denominator. How do you check if you have the correct graph? Using the coordinate of each point, substitute into the original equation. Does it produce true statements?