1. 4-2 Writing Linear Equations Given the Slope and a Point
Goals:
Use slope and any point on a line to write an equation of the line.
Write an equation that models a real-life situation.
Eligible Content:
A / A / A / A / A / A / A

2. Steps: Plug what you are given into y = mx + b Solve for b.
Write the equation by plugging in m and b.

3. Write an equation of the line that passes through (6, -3) and has a slope of -2. y = mx + b = ‧ + b -3 = + b = b y = x + x y m -3 -2 6
-12 -2 9

4. Examples Write an equation in slope-intercept form. (-3,0), m =
y = x + 1
y = -2x +14
y = 6x + 10

5. Write an equation of a line that passes through
(1, 4) and has a slope of –3.
A. y = –3x + 4
B. y = –3x + 1
C. y = –3x + 13
D. y = –3x + 7

6. Practice
Page 229 #1-4

7. Word Problems Slope (m) still means rate of change (y per x)
y-intercept (b) still means beginning amount
Any other numbers will be paired up as an ordered pair (x, y).

8. Word Problems
y per x – the term used to figure out which value is x and which value is y when looking at the slope in a word problem.
To determine which # is x and which # is y, look at the slope!
If slope says balloons per week:
y=balloons, x = weeks
If slope says $ per hour:
y is $, x = hours

9. Word Problem #1
Betty withdraws $8.25 per week from her bank account. After 10 weeks, her balance is $534.
Write an equation in slope-intercept form that models this situation.
y = -8.25x
What will her balance be after 20 weeks?
$451.50

10. Word Problem #2
Employees at a store are given a $.40 raise each year. Jamie makes $7.15 after 3 years.
Write an equation in slope-intercept form that models this situation.
y = .40x
How much will she make after 5 years?
$7.95

11. Word Problem #3
Between , vacations increased by 26 million per year. In 1993, 740 million vacations were taken. Let x=0 correspond to
Write an equation in slope-intercept form that models this situation.
y = 26x + 532
How many vacations were taken in 2000?
922 million vacations

12. Homework
Page 229 #10-15
#9, 22, 45 do not graph