Lesson Presentation

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Lesson Presentation
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Learn to use slopes and intercepts to graph
linear equations.
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Insert Lesson Title Here
Vocabulary
x-intercept y-intercept slope-intercept form
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You can graph a linear equation easily by finding
the x-intercept and the y-intercept. The
x-intercept of a line is the value of x where the
line crosses the x-axis (where y 0). The
y-intercept of a line is the value of y where the
line crosses the y-axis (where x 0).
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In an equation written in slope-intercept form, y
mx b, m is the slope and b is the y-intercept.
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Example 4 Writing Slope-Intercept Form
Write the equation of the line that passes
through (3, 4) and (1, 4) in slope-intercept
form.
Find the slope.
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The slope is 2.
Substitute either point and the slope into the
slope-intercept form.
y mx b
Substitute 1 for x, 4 for y, and 2 for m.
4 2(1) b
4 2 b
Simplify.
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Example 4 Continued
Solve for b.
4 2 b
Subtract 2 from both sides.
2 2
2 b
Write the equation of the line, using 2 for m
and 2 for b.
y 2x 2
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Check It Out Example 4
Write the equation of the line that passes
through (1, 2) and (2, 6) in slope-intercept form.
Find the slope.
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The slope is 4.
Substitute either point and the slope into the
slope-intercept form.
y mx b
Substitute 1 for x, 2 for y, and 4 for m.
2 4(1) b
2 4 b
Simplify.
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Check It Out Example 4 Continued
Solve for b.
2 4 b
Subtract 4 from both sides.
4 4
2 b
Write the equation of the line, using 4 for m and
2 for b.
y 4x 2