# Parallel And Perpendicular Lines Worksheet Page 16

Slopes of Lines
Find slopes of lines.
Use slope to identify parallel and perpendicular lines.
Vocabulary
is slope used in transportation?
slope
rate of change
conditions. The sign at the right indicates a hill with a
6 feet vertically for every 100 horizontal feet traveled.
SLOPE OF A LINE
y
The
slope
of a line is the ratio
of its vertical rise to its horizontal run.
v
e
r
t
ic
a
l
r
i
s
e
slope
vertical rise
ho
r
i
z
o
n
t
a
l
r
u
n
horizontal run
In a coordinate plane, the slope of a line is the ratio of the
O
x
change along the y-axis to the change along the x-axis.
Slope
TEACHING TIP
The slope m of a line containing two points with coordinates (x
, y
) and (x
, y
) is
1
1
2
2
given by the formula
y
y
2
1
m
, where x
x
.
1
2
x
x
2
1
The slope of a line indicates whether the line rises to the right, falls to the right, or
is horizontal. The slope of a vertical line, where x
x
, is undefined.
1
2
Find the Slope of a Line
Example
Example
1
1
Find the slope of each line.
Study Tip
a.
b.
y
y
Slope
( 1,
)
2
Lines with positive slope
( 4,
)
rise as you move from left
0
to right, while lines with
O
x
O
x
( 0,
)
1
negative slope fall as you
move from left to right.
( 3,
)
2
r
i
s
e
Use the
method.
Use the slope formula.
r
u
n
From ( 3,
2) to ( 1, 2),
Let ( 4, 0) be (x
, y
) and
1
1
go up 4 units and right 2 units.
(0,
1) be (x
, y
).
2
2
y
y
r
i
s
e
4
2
1
or 2
m
r
u
n
2
x
x
2
1
1
0
1
or
0
(
4)
4
Lesson 3-3 Slopes of Lines 139