Notes with answers - Summit Schools

2.3
Your Notes
When calculating
the slope, be sure
to subtract the
x‑coordinates and
the y‑coordinates
in the correct order.
A vertical line has
“undefined slope”
because for any
two points, the
slope formula’s
denominator
becomes 0, and
division by 0 is
undefined.
Slope and rate of change
Goal p Find and use the slope of a line.
Vocabulary
Slope For a nonvertical line, the ratio of the line’s
vertical change to its horizontal change
ThE SlopE oF a linE
The slope m of the nonvertical line passing through
the points (x1 , y1 ) and (x2 , y2 ) is given by the formula
m 5 y2 2 y1 } .
x2 2 x1 Example 1 Find the Slope of a Line
Find the slope of the line through (1, 3) and (6, 7).
Solution
Let (x 1 , y 1 ) 5 (1, 3) and (x 2 , y 2 ) 5 (6, 7) .
m 5 y2 2 y1 } 5
x2 2 x1 7 2 3
}
6 2 1
The slope of the line is
4
5 }
5
4
} .
5
claSSiFyinG linES by SlopE
Positive Negative Zero Undefined
O
y
x
O
y
Line rises from Line falls from Line is Line is
left to right. left to right . horizontal . vertical .
30 Lesson 2.3 • Algebra 2 C&S Notetaking Guide Copyright © McDougal Littell/Houghton Mifflin Company
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