Download a) Find a slope-intercept equation for the line with slope 2 that

EXTRA PRACTICE 9
Writing Equations of Lines
Use after Section 3.7
NAME_________________________________
______________________________________________________________________________________
Examples:
a) Find a slope-intercept equation for the line with slope 2 that contains ( 0,5 ) .
y = mx + b
y = 2x + 5
The slope-intercept equation.
Substitute 2 for m and 5 for b.
b) Find a slope-intercept equation for the line with slope 2 that contains ( 3, −1) .
y − y1 = m ( x − x1 )
Write the point-slope equation
y − ( −1) = 2 ( x − 3)
with x1 = 3, y1 = −1 .
y +1 = 2x − 6
y = 2x − 7
Solve for y to write a slope-intercept equation.
This is the slope-intercept equation.
c) Find an equation of a line that contains the points ( 5, −2 ) and ( −2,1) .
m=
1 − ( −2 )
3
3
=
=−
7
−2 − 5 −7
y − ( −2 ) = −
3
( x − 5)
7
First find the slope.
Use the point-slope equation y − y1 = m ( x − x1 ) and
substitute −
3
for m, 5 for x1 , and −2 for y1 .
7
3
15
y+2=− x+
7
7
(We could have substituted −2 for x1 and 1 for y1 .)
3
15 14
y = − x+ −
7
7 7
Solve for y to write a slope-intercept equation.
3
1
y = − x+
7
7
This is the slope-intercept equation.
Find a point-slope equation for a line containing the given point and having the given slope.
1.
( 4, −3) , m = −1 __________________
2.
( −5, −6 ) , m = 2
3.
( −7, 2 ) , m = 3 ___________________
4.
( 3,5) , m = −2
_____________________
______________________
Find a slope-intercept equation for a line containing the given point and having the given slope.
6. ( 5, −2 ) , m = 2 ______________________
5. ( 6, −2 ) , m = −3 _________________
7.
( 7, 0 ) , m = 4
9.
( 5, −1) , m =
____________________
1
5
_________________
8.
( 0,9 ) , m = −2
______________________
10.
( −3, −2 ) , m =
1
_____________________
4
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EXTRA PRACTICE 9 (continued)
Writing Equations of Lines
Use after Section 3.7
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Find an equation of the line that contains the given pair of points.
11.
(1,5) and ( 4,2 )
_________________
12.
( −4, 2 )
13.
( −5, −3)
15.
( −8,3) and ( −4,1)
17.
(1,3)
19.
( −7, 4 ) and ( −4, 7 )
and (1, −1) ______________
14.
( 0,3) and ( −2, 6 )
___________________
_______________
16.
( 6, 2 ) and ( −3, 0 )
___________________
and ( 4, 6 ) _________________
18.
( 3, −4 ) and ( −3, 4 )
__________________
20.
( 9, −5)
______________
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and (1, −3) __________________
and ( 7, 7 ) ___________________