5.2
Point-Slope Form
How much pressure is on a diver?
Goal
Use point-slope form to
write the equation of a
line.
As you saw in Developing
Concepts 5.2, page 276, you
can write an equation of a line
given the slope and a point on the
line. In Exercise 44 you will write
an equation that models the
pressure on a diver.
Key Words
• slope
• point-slope form
POINT-SLOPE FORM
The point-slope form of the equation of the line through (x1, y1)
with slope m is y y1 m(x x1).
Student Help
Point-Slope Form from a Graph
1
EXAMPLE
Write the equation of the line in the
graph in point-slope form.
5
Solution
3 (1, 2)
STUDY TIP
Use the given point (1, 2). From the
Remember that you
can calculate slope as
graph, find m .
y
3
2
3
rise
m .
run
1
y y1 m(x x1)
3
5
x
Write point-slope form.
2
3
2
3
y 2 (x 1)
ANSWER 䊳
2
Substitute for m, 1 for x1, and 2 for y1.
2
3
The equation y 2 (x 1) is written in point-slope form.
Point-Slope Form from a Graph
Write the equation of the line in point-slope form.
1.
2.
y
1
(0, 0)
3.
y
3
3
2
–1 x
(3, 2)
Chapter 5
Writing Linear Equations
1
3
(3, 1)
5
2
1
1
278
y
5 x
1
2
x