The Standard And Point Slope Forms Page 2
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Skill B
Writing an equation of a line in point-slope form
Recall The point-slope form for an equation of a line is
y
y
m(x
x
)
.
1
1
Example
Write an equation for the line through (1,
1
) and (
1
, 5)
a. in point-slope form.
b. in slope-intercept form.
Solution
a. First find m.
difference in y-values
1
5
6
m
3
difference in x-values
1
( 1)
2
Substitute the slope and one of the points into the point-slope equation.
y
y
m(x
x
)
1
1
y
( 1)
3(x
1)
Use the point (1,
1
).
y
1
3(x
1)
Simplify.
b. Rewrite the equation in the form
y
mx
b
.
y
1
3(x
1)
y
1
3x
3
Distributive Property
y
3x
2
Subtract 1 from each side.
Write an equation for each line in point-slope form.
1
7. containing (4,
1
) and with a slope of
2
8. crossing the x-axis at
x
3
and the y-axis at
y
6
9. containing the points
( 6,
1)
and (3, 2)
Rewrite each equation in slope-intercept form.
10. the line from Exercise 7
11. the line from Exercise 8
12. the line from Exercise 9
13. In what situations would you find it easier to use point-slope
form, and in what situations would you find it easier to use
slope-intercept form?
60
Reteaching Masters
Algebra 1
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