1. 4-1 Writing Linear Equations in Slope-Intercept Form
Goals:
Use the slope and y-intercept to write the equation of a line.
Model a real-life situation with a linear equation.
Eligible Content:
A / A / A / A / A / A / A

2. Example
Write the equation of the line whose slope is -2 and whose y-intercept is 5. y = mx + b y = x + y = -2x + 5 m b -2 5

3. Examples Write an equation in slope-intercept form.
Slope is 3, y-intercept is -5
y = 3x – 5
m = -3, b = 6
y = -3x + 6
Slope is – ½, y-intercept is -4
y = - ½ x – 4

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

5. Write the equation of each graph.1. 2.

6. Example #3
Which of the following is an equation in slope-intercept form for the line shown in the graph? A. B. C. D.

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

8. Practice Write an equation in slope-intercept form. m = 5, b = 8
Slope is 6, y-intercept is – 3
b = 4, m = ¼
y-intercept is 2, slope is -6
m = 1, b = 0
y = 5x + 8
y = 6x – 3
y = ¼ x + 4
y = -6x + 2
y = x

9. Word Problems Slope is rate of change!!!
Look for words like per, for each, for every…
y-intercept is the beginning amount
Look for words like beginning, initial…

10. Word Problem #1
Your family decides to rent bikes while you are on vacation. It costs $4 to rent the bike, plus $1.50 per hour.
Write an equation in slope-intercept form that models this situation.
y = 1.5x + 4
How much will it cost to rent the bike for 12 hours?
$22

11. Word Problem #2
In 1990, the population in California was million. During the next 25 years, the population increased by .31 million people per year.
Write an equation in slope-intercept form that models this situation.
y = .31x
How many people were there in California in 2005?
34.41 million people

12. Word Problem #3
A telephone call costs $3.44 for the first minute, and $.24 for each additional minute.
Write an equation in slope-intercept form that models this situation.
y = .24x
How much will it cost for a 9 minute phone call?
$5.36

13. 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 D spent for any year n since 1986.
A. D = 0.15n
B. D = 0.15n + 3
C. D = 3n
D. D = 3n

14. 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

15. Homework
Pages #11-22
#37, 50,51
You do not have to graph any equations!