Page 132 - Math Course 3 (Book 1)

Slope-Intercept Form Equations
Mo. 4

Lesson 3 Let’s Begin

KEY CONCEPTS:
1. Write and graph linear equations in slope- Write an Equation Given Slope and y-Intercept
intercept form.
2. Model real-world data with an equation in Example
slope-intercept form.

Write an equation in slope-intercept form of the line
1
with a slope of and a y-intercept of –6.
MO. 4 - L3a 4
y = mx + b Slope-intercept form
Write and Graph Slope-Intercept 1 1
4
4
Form Equations y = – x – 6 Replace m with and b with
–6
slope-intercept form 1
Answer y = – x – 6
An equation of the form y = mx + b, where m is the 4
slope and b is the y-intercept, is in slope-intercept
form.
Write an Equation From a Graph
y
Example

(0, b)
y = mx + b Write an equation in slope-intercept form of the line
shown in the graph.

x Step 1
0 You know the coordinates of two points on the line.
Find the slope.

Key Concept Let (x , y ) = (0, –3) and (x , y ) = (2, 1).
2
2
1
1
Slope-Intercept Form

Words The linear equation y = mx + b is written in
slope-intercept form, where m is the slope
and b is the y-intercept.
Symbols Graph
y = mx + b y

y – y rise
m = 2 1
(0, b) x – x 1 run
2
Slope
y = mx + b m = 1–(–3) (x , y ) = (0, –3)
1
1
Y-intercept 2 – 0 (x , y ) = (2, 1)
2
2
x m = 4 or 2 Simplify.
0 2
The slope is 2.
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