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Warm-Up
Evaluate for x = -1, 0, and 2.
1. f(x) = 3x – 7
2. f(x) = -2x + 12
5.1
Objectives:1. Write linear equations given m and b.2. Use linear equations in real life.
Vocabulary: Slope-intercept Form
Writing Linear Equations in Slope-Intercept Form
5.1
Slope-intercept Form:
m = b =
y = mx + b
Writing Linear Equations in Slope-Intercept Form
5.1
slope of a line =
y- intercept (0, b)
riserun
Reviewing Chapter 4
Find the slope and y-intercept of these:
y = 2x + 5
m = b =
Reviewing Chapter 4
Find the slope and y-intercept of these:
y = -x – 3
m = b =
Reviewing Chapter 4
Find the slope and y-intercept of these:
y = 4
m = b =
What kind of line is
this?
Reviewing Chapter 4
Find the slope and y-intercept of these:
y = ½x + 4
m = b =
Reviewing Chapter 4
Find the slope and y-intercept of these:
y = 3 – 7x
m = b =
y = mx + b
Writing Linear Equations in Slope-Intercept Form
5.1
How to find the equation of a line:
1. Find the slope (m) of the line.2. Find the y-intercept (b) of the line.3. Plug these values into y = mx + b
m = 4 b = 3
y = 4x + 3
Example 1 Writing an Equation of a Line
Write the equation of the line whose slope m = -2 and whose y-intercept b = 5.
y = mx + b
Example 1 Writing an Equation of a Line
Write the equation of the line whose slope and whose y-intercept .
y = mx + b
2m
3 b 2
Example 1 Writing an Equation of a Line
Write the equation of the line whose slope and whose y-intercept .
y = mx + b
4m
5 (0, 4)
Example 1 Writing an Equation of a Line
Write the equation of the line whose slope m = 1 and whose y-intercept b = 7.
y = mx + b
Example 2 Writing an Equation of a Line from a Graph
Write the equation of the line shown in the graph.
1 2 3 4 5 6 7
123
56
4
7
-6
-2
-4
-6-4 -2y = mx + b
Purple:
Blue:
Pink:
Orange:
Example 3 A Linear Model for Population
The number of trout in a lake was estimated to be 44.5 thousand in 1995. During the next 10 years, the trout population is expected to increase by about 3.2 thousand per year. Write a linear equation to model the trout population in any year between 1995 and 2005. Let t be the number of years since 1995.
Predict the trout population in 2002.
P = 3.2t + 44.5
≈ 66.9 thousand trout
Guided Practice
Please complete #3-11 on pg. 276 in your textbook. Raise your hand when you are done.
3. 9.
4. 10.
5.
6.
7.
8. 11.
5.1
To be turned in for a classwork grade!
Tonight’s Homework
pg. 276#’s 12-19 all, 21-29 odd