SWBAT… Write lines in slope-intercept form Wed, 2/20/10

Agenda1. Warm-up (10 min)2. Notes on slope intercept – 4 examples (30 min)3. Exit slip (5 min)

WARM-UPhttp://nlvm.usu.edu/en/nav/frames_asid_332_g_4_t_2.html?from=category_g_4_t_2.html

HW#3: Writing equations in slope-intercept form

Slope-intercept form:Slope-intercept form:Slope-intercept form:Slope-intercept form:

What is the slope? ____________

2 1y x Now look at the equation below……

What is the y-intercept? ____________

Given y = ½x + ¾, what is the slope and the y-intercept?

m = ½b = ¾

Given y = ½x – ¾, what is the slope and the y-intercept?

m = ½b = -¾

Given y = -½x – ¾, what is the slope and the y-intercept?

m = -½b = -¾

• y = mx+ b is an equation that defines a line

• A line has two characteristics1. Slope2. Points that fall on the line

Converting linear Converting linear equations into Slope-equations into Slope-

Intercept FormIntercept Form

4 Examples 4 Examples

Converting linear Converting linear equations into Slope-equations into Slope-

Intercept FormIntercept Form

4 Examples 4 Examples

Slope intercept form is:

y = mx + b

Our main goal is to get the y alone on one side of the

equation

Example 1 - convert into slope-intercept Example 1 - convert into slope-intercept formform

Example 1 - convert into slope-intercept Example 1 - convert into slope-intercept formform

2 4 2y x 2 2 2

(divide both sides by 2 to get y alone)

(now simplify all fractions)

2 1

2 1y x

Slope (m) = 2

y-intercept (b) = 1

(divide both sides by 5 to get y alone)

(now simplify all fractions)

y = 2x + 3 BRAVO!!

Slope (m) = 2

y-intercept (b) = 3

5y = 10x + 15

*** Your turn – Example 2 – convert

into slope-intercept form ***

5 5 5

2 3

*** Your turn – Example 3 – convert

into slope-intercept form ***

-3y = -9x – 12Step 1: divide both sides by -3 to get y alone

Step 2: Simplify all fractions

Step 3: Write your equation in y = mx + b

Slope (m) =

y-intercept (b) =

*** Check Your Answer ***

(divide both sides by -3 to get y alone)

(now simplify all fractions)

y = 3x + 4

-3y = -9x – 12-3 -3 -3

Slope (m) = 3

y-intercept (b) = 4

21x – 7y = 14(subtract both sides by 21x)

-7y = -21x + 14 (divide both sides by -7)

y = 3x – 2(simplify all fractions)

Slope (m) = 3

y-intercept (b) = -2

Example 4 - convert into slope-intercept Example 4 - convert into slope-intercept formform

Example 4 - convert into slope-intercept Example 4 - convert into slope-intercept formform

-21x -21x

-7 -7 -7

3 2

2y + 26 = -6xStep 1: Subtract both sides by 26

Step 2: Divide both sides by 2 to get y by itself

Step 3: Simplify all fractions

***EXIT SLIP ***

Slope (m) =

y-intercept (b) =

2y + 26 = -6x(subtract both sides by 26)

2y = -6x – 26(now divide both sides by 2

y = -3x – 13

(simplify all fractions)

*** Check Your Answer ***

26 -26

2 2 2

Slope (m) = -3

y-intercept (b) = -13