1. Write and graph linear equations in slope-intercept form.
Model real-world data with an equation in slope-intercept form.
slope-intercept form
Lesson 3 MI/Vocab

2. BrainPOP: Slope and Intercept
Lesson 3 Key Concept 1

3. Write an Equation Given Slope and y-Intercept
Write an equation in slope-intercept form of the line whose slope is and whose y-intercept is –6.
Slope-intercept form
Answer:
Lesson 3 Ex1

4. 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 A B C D
Lesson 3 CYP1

5. Write an Equation From a Graph
Write an equation in slope-intercept form of the line shown in the graph.
Step 1 You know the coordinates of two points on the line. Find the slope. Let (x1, y1) = (0, –3) and (x2, y2) = (2, 1).
(x1, y1) = (0, –3)
(x2, y2) = (2, 1)
Lesson 3 Ex2

6. Write an Equation From a Graph
Simplify.
The slope is 2.
Step 2 The line crosses the y-axis at (0, –3). So, the y-intercept is –3.
Step 3 Finally, write the equation.
y = mx + b
Slope-intercept form
y = 2x – 3
Simplify.
Answer: The equation of the lines is y = 2x – 3.
Lesson 3 Ex2

7. Write an equation in slope intercept form of the line shown in the graph.B. C. D. A B C D
Lesson 3 CYP2

8. Step 1 The y-intercept is –7. So graph (0, –7).
Graph Equations
A. Graph y = 0.5x – 7.
Step 1 The y-intercept is –7. So graph (0, –7).
Step 2 The slope is 0.5
From (0, –7), move up 1 unit and right 2 units. Draw a dot.
Step 3 Draw a line through the points.
Lesson 3 Ex3

9. Step 1 Solve for y to write the equation in slope-intercept form.
Graph Equations
B. Graph 5x + 4y = 8.
Step 1 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.
Lesson 3 Ex3

10. Divide each term in the numerator by 4.
Graph Equations
Divide each term in the numerator by 4.
Step 2 The y-intercept of
So graph (0, 2).
Lesson 3 Ex3

11. From (0, 2), move down 5 units and right 4 units. Draw a dot.
Graph Equations
Step 3 The slope is
From (0, 2), move down 5 units and right 4 units. Draw a dot.
Step 4 Draw a line connecting the points.
Answer:
Lesson 3 Ex3

12. A. Graph y = 2x – 4.
A. B.
C. D. A B C D
Lesson 3 CYP3

13. B. Graph 3x + 2y = 6.
A. B.
C. D. A B C D
Lesson 3 CYP3

14. Write an Equation in Slope-Intercept Form
A. HEALTH The ideal maximum heart rate for a 25-year-old who is exercising to burn fat is 117 beats per minute. For every 5 years older than 25, that ideal rate drops 3 beats per minute. Write a linear equation to find the ideal maximum heart rate for anyone over 25 who is exercising to burn fat.
Lesson 3 Ex4

15. Write an Equation in Slope-Intercept Form
ideal rate Ideal rate of years older for 25- rate equals change times than 25 plus year-old.
Words
Variables
Equation
Let R = the ideal heart rate.
Let a = years older than 25.
R = × a
Answer:
Lesson 3 Ex4

16. Write an Equation in Slope-Intercept Form
B. Graph the equation.
The graph passes through (0, 117) with a slope of
Answer:
Lesson 3 Ex4

17. Write an Equation in Slope-Intercept Form
C. Find the ideal maximum heart rate for a person exercising to burn fat who is 55 years old.
The age 55 is 30 years older than 25. So, a = 30.
Ideal heart rate equation
Replace a with 30.
Simplify.
Answer: The ideal heart rate for a 55-year-old person is 99 beats per minute.
Lesson 3 Ex4

18. A. The amount of money spent on Christmas gifts has increased by an average of $150,000 ($0.15 million) per year since Consumers spent $3 million in Write a linear equation to find the average amount spent for any year since 1986.
A. D = 0.15n
B. D = 0.15n + 3
C. D = 3n
D. D = 3n A B C D
Lesson 3 CYP4

19. B. The amount of money spent on Christmas gifts has increased by an average of $150,000 ($0.15 million) per year since Consumers spent $3 million in Graph the equation.
A B.
C D. A B C D
Lesson 3 CYP4

20. C. The amount of money spent on Christmas gifts has increased by an average of $150,000 ($0.15 million) per year since Consumers spent $3 million in Find the amount spent by consumers in 1999.
A. $5 million
B. $3 million
C. $4.95 million
D. $3.5 million A B C D
Lesson 3 CYP4