Warm Up

The senior class is selling tickets for a car wash to raise money for Grad Nite. Since pickup trucks, vans, and SUVs are bigger vehicles they are charged more than cars. Write an equation to model how much money was raised.

What information do you need to solve the problem?

•The price cars are charged.

•The number of cars washed.

•The price of vans, SUVs, and trucks are charged.

•The number of vans, SUV’s, and trucks washed.

•How much money is raised.

$4.00

$6.00

$600.00

c

t

On page 82 complete the investigating slope and y-intercept

2y 3x 6

y 3

2x 3

2.3: Quick Graphs of Linear Equations, p. 82

Slope-Intercept Form

y = mx + bm = slope

b = y-intercept

3x − 2y = 6−3x −3x

−2 −2

Example 0 Put the following equation in slope-intercept form.

−2

+3

+2

−3

x

y

1) Find the slope and y-intercept.

2) Plot the y-intercept.

m = −23

or m = 2

4) Draw a line through the points.

y 2

3x 2

3) Plot the slope.

−3

2;

3m b 2

Example 1a Graph the following linear equation using the slope and y-intercept

2.3: Quick Graphs of Linear Equations, p. 82

2.3: Quick Graphs of Linear Equations, p. 82

Example 2 You buy a $1200 stereo on the layaway plan at your local Wally World. You put $200 down and then make payments of $40 a week until it’s paid off.

A. Write an equation to model the situation.B. Graph the model.

A. a = −40t + 1000a = amount owedt = time in weeks

B.

200

400

600

800

1000

1200

5 10 15 20 25 30

Am

ount

Ow

ed

Number of Weeks

Standard Form (Ax + By = C)The easiest method for graphing a line in Standard Form is finding the x and y-intercepts.

x-intercept = where the line crosses the x-axis

y-intercept = where the line crosses the y-axis

Graph 3x + 2y = 6

x

yx-intercept y-intercept(set y = 0)

3x + 2(0) = 63x = 6x 2

(set x = 0)

2y = 6

y = 3

3(0) + 2y = 6

2.3: Quick Graphs of Linear Equations, p. 82

Example 3

Graphing Horizontal and Vertical Lines

y

x

y

x

Graph y = 1 and x = −2.

y = 1 x = −2

Count up 1 on the y-axis. Count left 2 on the x-axis.

p

2.3: Quick Graphs of Linear Equations, p. 82

Example 4

y = 1 x = −2

Draw a horizontal line. Draw a vertical line.

Horizontal Lines are in the form y = c.

Vertical Lines are in the form x = c.