Download 2 Write an Equation in Point-Slope Form 3 Use Point

Student Help
STUDY TIP
The point-slope form
y y1 m(x x1)
has two minus signs.
Be sure to account for
these signs when the
point (x1, y1) has
negative coordinates.
EXAMPLE
2
Write an Equation in Point-Slope Form
Write in point-slope form the equation of the line that passes through the point
(1, 5) with slope 3.
y y1 m(x x1)
Write the point-slope form.
Substitute 1 for x1, 5 for y1, and 3 for m.
y (5) 3(x 1)
y 5 3(x 1)
Simplify the equation.
ANSWER 䊳
The equation in point-slope form of the line is y 5 3(x 1).
Write an Equation in Point-Slope Form
4. Write in point-slope form the equation of the line that passes through the
1
point (2, 2) with slope .
2
EXAMPLE
3
Use Point-Slope Form
Write in slope-intercept form the equation of the line that passes through the
point (3, 7) with slope 2.
Student Help
Solution
y y1 m(x x1)
STUDY TIP
Write the point-slope form.
Notice that the equation
in Step 3 of Example 3
is in point-slope form.
Steps 4 and 5 convert
the equation to slopeintercept form.
Substitute 2 for m, 3 for x1, and 7 for y1.
y 7 2[x (3)]
Simplify the equation.
y 7 2(x 3)
Distribute the 2.
y 7 2x 6
Add 7 to each side.
y 2x 1
ANSWER 䊳
The equation of the line in slope-intercept form is y 2x 1.
CHECK ✓ In general, you can use
a graph to check whether your
answer is reasonable.
In the graph at the right, notice
that the line y 2x 1 has a
slope of 2 and passes through
the point (3, 7).
y
1
(3, 7)
7
2
5
3
y 2x 1
1
5
3
1
x
Use Point-Slope Form
5. Write in slope-intercept form the equation of the line that passes through the
point (2, 4) with slope 3. Check your answer by graphing.
5.2
Point-Slope Form
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