Download The Slope of a Line

4.6
Quick Graphs Using
Slope-Intercept form
• Objective 1 – Graph a linear
equation in slope-intercept form
Slope-Intercept form of the equation of a line
y
The linear equation
y = mx + b is written
y = 2x + 3
in
slopeSlope is 2
intercept form.
The slope of the
line is m.
The y-intercept is b.
y-intercept is 3
x
EXAMPLE 1
Writing equations in slopeintercept form
Equation
Slope
y-intercept
a) y = x + 2
m=1
b=2
b) y = -3x – 4
m = -3
b = -4
c) y = 3
m=0
b=3
d) y = -x
m = -1
b=0
m = -2
b=6
e) 2x + y = 6
-2x
Rewrite (subtract 2x)
-2x
y = -2x + 6
EXAMPLE 2
Graphing Using Slope and
y-intercept
Graph the equation y = 2x + 4
Find the slope and the y-intercept
2
m =2 or
b=4
1
Plot the y-intercept
Use slope to plot second
point
y
1
2
Draw a line through the two
points
x
If two lines have the same slope
then they are parallel
y = 2x + 1
EXAMPLE 3
You try it
Graph the equation y = 3x - 1
Find the slope and the y-intercept
3
m =3 or
1
y
b = -1
Plot the y-intercept
Use slope to plot second
point
1
Draw a line through the two
points
3
x
EXAMPLE 4
You try it
2
Graph the equation y   x  2
3
Find the slope and the y-intercept
m = 2
3
b=2
y
Plot the y-intercept
Use slope to graph second
point
Draw a line through the two
points
-2
x
3