Teacher
Algebra 3
Lesson 1.1
 Denoted as m
Objectives:
SSBAT define slope.
SSBAT calculate slope given 2 points.
SSBAT determine the slope of a line from the graph.
SSBAT determine if a line increases/decreases by analyzing
the slope.
Standards:
Slope of a Line
M11.A.1.1.3 and M11.D.3.2.3
 Measures how steep the line is
- the greater the slope the steeper the line
 Rate of Change
 Ratio of Vertical Change over Horizontal Change
Positive Slope
Horizontal Lines
The line will be going UPHILL from left to right.
The slope is ZERO
m=
#
Negative Slope
The line will be going DOWNHILL from left to right.
Vertical Lines
The slope is UNDEFINED
m=
#
Finding Slope of a Line from the graph
Finding Slope of a Line from the graph
m=
Rise
Run
1. Find 2 points on the Graph
2. Find the Vertical Change (rise) by counting the
number of units up/down from one point to the next
3. If you go up the number is positive
If you go down the number is negative
4. Find the Horizontal change (run) by counting the
number of units left/right from one point to the next
5. If you go right the number is positive
If you go left the number is negative
6. Form a fraction of
7. Simplify if possible, but leave as a fraction
1
Teacher
Examples: Find the slope of the given line.
2.
Down 2, Right 1
1.
m=
2
1
m = -2
Up 2, Right 3
m=
Finding Slope given 2 points on the line.
3.
Undefined
(x1 , y1) and (x2 , y2) are points on a line
 The slope of a
vertical line is always
undefined
y2  y1
x2  x1
m
 Reduce the fraction in the end if you can
1. Find the slope of the line containing the points
(-2,0) and (3,1)
m=
m=
 Does the line go uphill or downhill from left to right?
The line will go UPHILL because the slope is positive.
2. Find the slope of the line containing the points
(0,4) and (1,-1).
m
1 4
1 0
m
5
1
m  5
 Does the line go uphill or downhill from left to right?
The line will go Downhill because the slope is
negative.
2
Teacher
3. Find the slope of the line containing the points
(- 1,2) and (2,2)
m
22
2  ( 1)
m
4. Find the slope of the line containing the points
(-3,4) and (-3,-5)
m 
0
3
54
 3  (  3)
m
m 0
9
0
m  Undefined
Is the line a Horizontal or Vertical Line?
Is the line a Horizontal or Vertical Line?
 Horizontal because the slope is 0
 Vertical because the slope is Undefined.
The slope of a line is ⁄ and the line contains
the points (n, 9) and (-7, 1). What is the value
of n?
Give an example of two points that would
create a line to be undefined.
 Recall a line with an undefined slope means 0
is in the denominator
Answer: Any 2 ordered pairs that have the
same x-coordinate.
One example: (5, 8) and (5, 12)
Answer:
n=5
On Your Own
1. Find the slope of the line through the points
2) and (-3, 5)
(7,
3
10
Homework
Worksheet 1.1
2. Does the line that goes through the points above
increase or decrease? How do you know?
Decrease – the slope is negative
3