Equation of Lines

1
Equation of Lines

• Objectives
• Discover the slope intercept form of the
  equation of a line.

2
This graph shows the relationship between degrees
Celcius and degees Fahrenheit.
This is the graph of
3
To convert from C to F, pick some degrees
Celcius to convert
4
Lets say you want to convert 16C to F.
Find 16C on the x axis
5
Go straight up from 16 to the line.
6
From the line, go to the f axis. This is equal
to 16C in Fahrenheit!
16 C 61F
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16C is equal to almost 61 Fahrenheit
16 C 61F
8
You plug 16C into the equation and see what you
get.
9
You will now be asked several questions about the
graph of
10
37
3C ___F
11
Plug 3C into the equation and see what you get.
12
48
9C ___F
13
107.6
42C _____F
14
5
42F _____C
15
38
100F ____C
16

y 3x 2
Complete the chart and calculate the slope of the
line.
x
-2
-1
0
1
2
y
-4
5
2
8
-1
17
Compare your calculated slope with the equation
of the line. Do you see a relationship?
y 3x 2
slope
x
-2
-1
0
1
-4
5
2
3x2
-1
18
Compare your calculated slope with the equation
of the line. Do you see a relationship?
y 3x 2
The slope is the number in front of the x.
slope
x
-2
-1
0
1
-4
5
2
3x2
-1
19
When an equation is in slope-intercept form
y mx b
slope
20
Now look at the graph of each line. Look at
where the graphs cross the y axis.
y 3x 2
21
What is the significance of this number in the
equation?
y 3x 2
22
This is the y-intercept (where the graph crosses
the y axis).
y 3x 2
23
When an equation is in slope-intercept form
y mx b
slope
y intercept
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Slope-Intercept Conjecture
C-23
ymxb
m slope
b y intercept
25
What is the equation of the line in
slope-intercept form?

m
b
-2
26
What is the equation of the line in
slope-intercept form?
m

3
b
27
What is the equation of the line in
slope-intercept form?

m
b
4
28
Graph the equation. First calculate the slope
and y-int.

m
-4
b
29
Plot the y-intercept.

m
-4
b
30
Apply slope from y-intercept.

m
-4
b
31
Draw line through two points.

m
-4
b
32
Graph each equation

m
1
b
33
Graph each equation

y-4x6
m
-4
b
6
34
True or False. The slope of the line below is
.
35
True or False. The y-intercept of the line is
-4.
It's 4, not -4.
36
True or False. The equation of the line is