1. Warm ups
What is the slope of the line that passes through (–4, 8) and (5, 2)?
Suppose y varies directly as x and y = –5 when x = 10. Which is a direct variation equation that relates x and y?
Find the next two terms in the arithmetic sequence –7, –4, –1, 2, ….
Is the function represented by the table linear? Explain.

2. 4-1 Graphing in slope intercept form
Objective: Write and graph linear equations in slope-intercept from.

3. Vocabulary
slope-intercept form y = mx + b

4. Slope-Intercept Form

5. Example 1
Write an equation in slope-intercept form of the line with a slope of and a y-intercept of –1. Then graph the equation.
Slope-intercept form
Write and Graph an Equation

6. Example 1 Graph Now graph the equation .
Step 1 Plot the y-intercept (0, –1).
Step 2 The slope is From (0, –1), move up 1 unit and right 4 units. Plot the point.
Answer:
Step 3 Draw a line through the points.
Write and Graph an Equation

7. Try with a Mathlete
Write an equation in slope-intercept form of the line whose slope is 4 and whose y-intercept is 3.
A. y = 3x + 4
B. y = 4x + 3
C. y = 4x
D. y = 4

8. Example 2
Graph 5x + 4y = 8.
Solve for y to write the equation in slope-intercept form.
5x + 4y = 8
Original equation
5x + 4y – 5x = 8 – 5x
Subtract 5x from each side.
4y = 8 – 5x
Simplify.
4y = –5x + 8
8 – 5x = 8 + (–5x) or –5x + 8
Divide each side by 4.
Graph Linear Equations

9. Example 2 Graph Slope-intercept form Answer: Now graph the equation.
Step 1 Plot the y-intercept (0, 2).
Step 2 The slope is
From (0, 2), move down 5 units and right 4 units. Draw a dot.
Step 3 Draw a line connecting the points.
Graph Linear Equations

10. Try with a Mathlete
Graph 3x + 2y = 6.
A B.
C D.

11. Example 3 Graph y = –7. Step 1 Plot the y-intercept (0, -7).
Step 2 The slope is 0. Draw a line through the points with the y-coordinate -7.
Answer:
Graph Linear Equations

12. TOO
Graph 5y = 10.
A. B.
C. D.

13. Example 4
Which of the following is an equation in slope-intercept form for the line shown in the graph? A. B. C. D.

14. TOO
Which of the following is an equation in slope-intercept form for the line shown in the graph? A. B. C. D.

15. Homework