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Writing Equations of Perpendicular Lines
Choose Course
Algebra 1
Writing Linear Equations
Writing Equations of Perpendicular Lines
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Writing Equations of Perpendicular Lines 1.1 - Solution
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Return to Writing Equations of Perpendicular Lines
a
If two lines are perpendicular, the product of the lines' slopes need to be equal to
-
1.
\text{-} 1.
-
1
.
m
1
⋅
m
2
=
-
1
m_1\cdot m_2 = \text{-}1
m
1
⋅
m
2
=
-
1
SubstituteII
m
1
=
9
m_1={\color{#0000FF}{9}}
m
1
=
9
,
m
2
=
-
0.1
m_2={\color{#009600}{\text{-} 0.1}}
m
2
=
-
0
.
1
9
⋅
(
-
0.1
)
=
?
-
1
{\color{#0000FF}{9}}\cdot ({\color{#009600}{\text{-} 0.1}}) \stackrel{?}{=} \text{-}1
9
⋅
(
-
0
.
1
)
=
?
-
1
UseCalc
Use a calculator
-
0.9
≠
-
1
\text{-} 0.9 \neq \text{-}1
-
0
.
9
=
-
1
The lines are not perpendicular.
b
Let's follow the same procedure, test if
m
1
⋅
m
2
=
-
1
m_1\cdot m_2=\text{-} 1
m
1
⋅
m
2
=
-
1
.
m
1
⋅
m
2
=
-
1
m_1\cdot m_2 = \text{-}1
m
1
⋅
m
2
=
-
1
SubstituteII
m
1
=
0.125
m_1={\color{#0000FF}{0.125}}
m
1
=
0
.
1
2
5
,
m
2
=
-
8
m_2={\color{#009600}{\text{-} 8}}
m
2
=
-
8
0.125
⋅
(
-
8
)
=
?
-
1
{\color{#0000FF}{0.125}}\cdot ({\color{#009600}{\text{-} 8}}) \stackrel{?}{=} \text{-}1
0
.
1
2
5
⋅
(
-
8
)
=
?
-
1
UseCalc
Use a calculator
-
1
=
-
1
\text{-}1 = \text{-} 1
-
1
=
-
1
These lines are perpendicular.
