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Unformatted text preview: hat if L1 passes through (−3, −4) and (0, 1), and if L2
passes through (0, 0) and (−4, 4), then L1 is not parallel to L2 . Outline Linear Equations Graphing Linear Equations The Slope of a Line Applications Perpendicular Lines
Deﬁnition
Two distinct lines are perpendicular if they intersect at right angles.
Theorem
Suppose L1 is a line with slope m1 and L2 is a line with slope m2 .
Then L1 is perpendicular to L2 if and only if m1 m2 = −1. In this
case we write L1 ⊥ L2 .
Example
A horizontal line is perpendicular to a vertical line.
Show that the points (−3, 7), (2, 2), and (5, 5) form a right
triangle. Outline Linear Equations Graphing Linear Equations The Slope of a Line Applications An Application Example
When empty, a large dumptruck gets about 15 miles per gallon of
fuel. It is estimated that for each 3 tons of cargo it hauls, fuel
mileage decreases by 3 miles per gallon.
4
1 If the dumptruck carries 10 tons of cargo, what is the truck’s
mileage? 2 If the truck is getting 10 miles per gallon, how much weight is
it carrying?...
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 Spring '14
 K.JPlatt
 Algebra, Linear Equations, Equations, Slope

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