Section 4.5_Point­Slope Form.notebook
June 08, 2011
Different Forms
Beginning & Intermediate
Algebra
4.5—Point-Slope Form
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Oct 8­9:11 AM
From Yesterday
Writing Equations of Lines
m=2
Remember: “m” is slope
y-intercept = (0,5)
Write an equation for the line whose slope is -2
through the point (0, 5)
Any time you need to write an equation USE POINTSLOPE FORM
BUT, this doesn’t always work!!
m = SLOPE
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(x1, y1) = SOME POINT
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What Do You Need?
Write an equation for the line whose slope is -2
through the point (0, 5)
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To write an equation of a
line you need a POINT
and a SLOPE
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Section 4.5_Point­Slope Form.notebook
June 08, 2011
Example
Example
Write an equation for the line with a slope of -3
passing through (1,2).
y1 = 2
x1 = 1
m = -3
Write an equation for the line through (3, -5) with a
slope of 2. Give the answer in both standard form and
slope-intercept form.
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Example
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Find the Slopes
Write the equation of the line through (-2, -3) and
(-5, 1). Give the answer in both standard form and
slope-intercept form.
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Parallel & Perpendicular Lines
Parallel lines have Slopes of
the SAME SLOPE perpendicular lines
are OPPOSITE
(signs)
RECIPROCALS
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Example
Are these lines parallel, perpendicular or
y = 3x + 2
5x – 3y = 11
y = 3x – 2
3x + 5y = 8
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Section 4.5_Point­Slope Form.notebook
June 08, 2011
Example
2x – 5y = 13
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Equation of a PARALLEL Line
Write an equation of the line through (-2, 1) and parallel to the
line y = -3x+1. Write the answer in slope-intercept form.
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3x + 2y = 9
Find the slopes of the
following:
Find the slopes of the
following:
Original Line:
Original Line:
Parallel Line:
Parallel Line:
Perpendicular Line:
Perpendicular Line:
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Equation of a PERPENDICULAR Line
Write an equation of the line through (3, 7) and parallel to the
line 5x + 2y = 3. Write the answer in slope-intercept form.
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