Student Help
Undefined Slope
Find the slope of the line that passes through the points (5, 1) and (5, 3).
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INT
5
EXAMPLE
Solution
Let (x1, y1) (5, 1) and (x2, y2) (5, 3).
y y
2
y
Subtract y-values.
2
1
m
x x
Use the same order
to subtract x-values.
1
3 (1)
55
31
55
Subtracting a negative
is the same as adding
a positive.
4
0
Division by zero is
undefined.
(5, 3)
1
Substitute values.
ANSWER 䊳
3
1
1
1
3
x
(5, 1)
3
The line is vertical.
The slope is undefined.
Because division by zero is undefined, the expression
4
has no meaning. The slope of the line is undefined.
0
Find the Slope of a Line
For each line, determine whether the slope is positive, negative, zero, or
undefined. If the slope is defined, find the slope.
7.
8.
y
5
(2, 4)
(4, 4)
3
(1, 4)
3
1
3
y
5
(2, 4)
3
(1, 1)
1
1
9.
y
5
5 x
(4, 2)
1
3
5 x
1
3
SUMMARY
Slopes of Lines
A line with positive
slope rises from left
to right.
y
A line with zero
slope is horizontal.
y
x
232
A line with negative
slope falls from left
to right.
Chapter 4
y
x
Graphing Linear Equations and Functions
A line with
undefined slope
is vertical.
y
x
x
5 x