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2.5 writing Equations of lines
Goal p Write linear equations.
Vocabulary
Point-slope form An equation of a line written in
the form y 2 y 1 5 m(x 2 x 1 ) where the line passes
through the point (x 1 , y 1 ) and has a slope of m
wriTinG an EquaTion oF a linE
Slope-Intercept Form Given the slope m and the
y-intercept b , use slope-intercept form: y 5 mx 1 b .
Point-Slope Form Given the slope m and a point
(x1 , y1 ) , use point-slope form: y 2 y1 5 m(x 2 x1 ) .
Example 1 Write an Equation Given Slope and y-Intercept
Write an equation of the
line shown.
y
Solution
1
From the graph, you can see
that the slope is m 5 2
O 2
3
}
2
.
Because the line intersects the
y-axis at ( 0, 1 ), the y-intercept
is b 5 1 .
Use the slope-intercept form to write an equation of
the line.
y 5 mx 1 b Use slope-intercept form.
y 5 2 3
}
2
x 1 1 Substitute 2 3
}
2
for m and 1 for b.
Copyright © McDougal Littell/Houghton Mifflin Company Lesson 2.5 • Algebra 2 C&S Notetaking Guide 37
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