Geometry Section 3.7 cont.“Writing Equations of Lines”
While the slope-intercept form for the equation of a line is very useful
in graphing, it is not nearly as useful for writing the equation of a line
(unless you happen to be given the slope and the y-intercept).
The point-slope form for the equation of a line is __________________
In this equation m is, again, the slope and x1 and y1 are ______________________
)( 11 xxmyy
line on the points any two
Example: Write an equation for the line in point-slope form.
1. slope of -1 and contains the point (-3, 9)
)3(19
)3(19
xy
xy
)( 11 xxmyy
Example: Write an equation for the line in point-slope form.
2. passes through the points (1, 4) and (-3, 8))( 11 xxmyy 1
4
4
13
48
m
)(1 11 xxyy )1(14 xy
Example: Write an equation for the line in point-slope form.
3. slope of 3 and a y-intercept of 15
)( 11 xxmyy
Example: Write an equation for the line in point-slope form.
4. passes through the point (5, 1) and is perpendicular to the line 2
3
5 xy
)( 11 xxmyy
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