grade 8 Graphs Using Slope-Intercept Form.ppt

Quick Graphs Using Slope-
Intercept Form

Important!!!
Important!!!
This is a big concept in Algebra 1.You
need to thoroughly understand this!
Slope – Intercept Form
y = mx + b
m represents the slope
b represents the y-intercept

Writing Equations
Writing Equations
When asked to write an equation,
you need to know two things –
slope (m) and y-intercept (b).
b
mx
y 


Example 1:
Example 1: Writing Equations
Writing Equations
Write an equation in slope-intercept form of the line
that has a slope of 2 and a y-intercept of 6.
To write an equation, you need two things:
slope (m) =
y – intercept (b) =
We have both!! Plug them into slope-intercept form
y = mx + b
y = 2x + 6
2
6

Writing Equations
Writing Equations
Write an equation in slope-intercept form
for the following:
1. 3.
2. 4.
2
1



b
m
2
3
2
1


b
m
4
0



b
m
4
5
.
0



b
m

Write the equation of a line that has a
Write the equation of a line that has a
y-intercept of -3 and a slope of -4.
y-intercept of -3 and a slope of -4.
1. y = -3x – 4
2. y = -4x – 3
3. y = -3x + 4
4. y = -4x + 3

To find the slope and y-intercept
To find the slope and y-intercept
of an equation, write the equation
of an equation, write the equation
in slope-intercept form: y = mx +
in slope-intercept form: y = mx +
b.
b.
Find the slope and y-intercept.
1) y = 3x – 7
y = mx + b
m = 3, b = -7

2) y = x
y = mx + b
y = x + 0
3) y = 5
y = mx + b
y = 0x + 5
2
3
2
3 m =
b = 0
2
3
m = 0
b = 5

4)
4) 5x - 3y = 6
5x - 3y = 6
5
3
m =
b = -2

5) 2y + 2 = 4x
5) 2y + 2 = 4x
Write it in slope-intercept form.
(y = mx + b)
2y + 2 = 4x
- 2 - 2
2y = 4x – 2
2 2 2
y = 2x - 1
m = 2
b = -1

Find the slope and y-intercept of
Find the slope and y-intercept of
y = -2x + 4
y = -2x + 4
1. m = 2; b = 4
2. m = 4; b = 2
3. m = -2; b = 4
4. m = 4; b = -2

Example 2:
Example 2: Graphing Using
Graphing Using
Slope and y-Intercept
Slope and y-Intercept
When given an equation, you can easily
graph it in slope-intercept form. All you
need is two things–
the slope (m) and y-intercept (b).

Graphing Using Slope
Graphing Using Slope
and y-intercept
and y-intercept
Step 1: Make sure the equation is
in slope-intercept form
Step 2: Find the slope and y-
intercept
Step 3: Plot the y-intercept
Step 4: Apply the slope (rise/run)
to the y-intercept

Review: Graphing with slope-intercept
Review: Graphing with slope-intercept
1. Start by graphing the
y-intercept (b = 2).
2. From the y-intercept,
apply “rise over run”
using your slope.
rise = 1, run = -3
3. Repeat this again from
your new point.
4. Draw a line through
your points.
1
-3
Start here
1
-3
y 
 1
3
x  2

Graph:
Graph:
3
2 
 x
y
Step 1: y=mx+b
Step 2: slope = 2 y-intercept = 3
Step 3: plot the y-intercept on a graph
Step 4: apply the slope

x
y
x
y




6
1
2
Graph the following equations:

Homework:
Homework:
Complete Study Guide for
Complete Study Guide for
Chapter 4
Chapter 4 
 due Tuesday,
due Tuesday,
November 19
November 19th
th

grade 8 Graphs Using Slope-Intercept Form.ppt

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