Warm-Up Exercises
1. Graph y < 2 x – 1.
3
ANSWER
2. You are running one ad that costs $6 per day and
another that costs $8 per day. You can spend no
more than $120. Name a possible combination of days
that you can run the ads.
ANSWER
Sample answer: 16 days of the $6 ad
and 3 days of the $8 ad
Warm-Up1Exercises
EXAMPLE
Graph a system of two linear inequalities
Graph the system of inequalities. y > –x – 2
y  3x + 6
SOLUTION
Graph both inequalities in the same
coordinate plane. The graph of the
system is the intersection of the two
half-planes, which is shown as the
darker shade of blue.
Inequality 1
Inequality 2
Warm-Up1Exercises
EXAMPLE
Graph a system of two linear inequalities
CHECK
Choose a point in the dark blue region, such
as (0, 1). To check this solution, substitute 0
for x and 1 for y into each inequality.
?
1>0–2
1 > –2
1 ? 0 + 6
16
Warm-Up2Exercises
EXAMPLE
Graph a system of three linear inequalities
Graph the system of inequalities. y > –1
x > –2
x + 2y  4
SOLUTION
Inequality 1
Inequality 2
Inequality 3
Graph all three inequalities in the same coordinate
plane. The graph of the system is the triangular region
shown.
Warm-Up
Exercises
GUIDED
PRACTICE
for Examples 1 and 2
Graph the system of linear inequalities.
1.
y<x–4
y  –x + 3
ANSWER
Warm-Up
Exercises
GUIDED
PRACTICE
for Examples 1 and 2
Graph the system of linear inequalities.
2.
y  –x + 2
y<4
x<3
ANSWER
Warm-Up
Exercises
GUIDED
PRACTICE
for Examples 1 and 2
Graph the system of linear inequalities.
3.
y > –x
y x–4
y<5
ANSWER
Warm-Up3Exercises
EXAMPLE
Write a system of linear inequalities
Write a system of inequalities for the shaded region.
SOLUTION
INEQUALITY 1: One boundary line
for the shaded region is y = 3.
Because the shaded region is
above the solid line, the inequality
is y  3.
INEQUALITY 2: Another boundary line for the shaded
region has a slope of 2 and a y-intercept of 1. So, its
equation is y = 2x + 1. Because the shaded region is
above the dashed line, the inequality is y > 2x + 1.
Warm-Up3Exercises
EXAMPLE
Write a system of linear inequalities
ANSWER
The system of inequalities for the shaded region is:
y3
y > 2x + 1
Inequality 1
Inequality 2
Warm-Up4Exercises
EXAMPLE
Write and solve a system of linear inequalities
BASEBALL
The National Collegiate Athletic Association (NCAA)
regulates the lengths of aluminum baseball bats used
by college baseball teams. The NCAA states that the
length (in inches) of the bat minus the weight (in
ounces) of the bat cannot exceed 3. Bats can be
purchased at lengths from 26 to 34 inches.
a. Write and graph a system of linear inequalities that
describes the information given above.
b. A sporting goods store sells an aluminum bat that
is 31 inches long and weighs 25 ounces. Use the
graph to determine if this bat can be used by a player
on an NCAA team.
Warm-Up4Exercises
EXAMPLE
Write and solve a system of linear inequalities
SOLUTION
a. Let x be the length (in inches) of the bat, and let y be
the weight (in ounces) of the bat. From the given
information, you can write the following inequalities:
x–y3
The difference of the bat’s length and weight can
be at most 3.
x ≥ 26
The length of the bat must be at least 26 inches.
x ≤ 34
The length of the bat can be at most 34 inches.
y≥0
The weight of the bat cannot be a negative number.
Graph each inequality in the system. Then identify the
region that is common to all of the graphs of the
inequalities. This region is shaded in the graph shown.
Warm-Up4Exercises
EXAMPLE
Write and solve a system of linear inequalities
b. Graph the point that
represents a bat that is 31 inches
long and weighs 25 ounces.
ANSWER
Because the point falls outside the solution
region, the bat cannot be used by a player on an
NCAA team.
Warm-Up
Exercises
GUIDED
PRACTICE
for Examples 3 and 4
Write a system of inequalities that defines the shaded
region.
4.
ANSWER
x ≤ 3, y > 2 x
3
1
Warm-Up
Exercises
GUIDED
PRACTICE
for Examples 3 and 4
Write a system of inequalities that defines the shaded
region.
5.
ANSWER
y ≤ 4, x < 2
Warm-Up
Exercises
GUIDED
PRACTICE
for Examples 3 and 4
6. WHAT IF? In Example 4, suppose a Senior League
(ages 10–14) player wants to buy the bat described in
part (b). In Senior League, the length (in inches) of the
bat minus the weight (in ounces) of the bat cannot
exceed 8. Write and graph a system of inequalities to
determine whether the described bat can be used by
the Senior League player.
ANSWER
x
y ≤ 8, x ≥ 26, x ≤ 34, y ≥ 0
The bat can be used.
Daily
Homework
Quiz
Warm-Up
Exercises
1.
Write a system of inequalities for the shaded
region.
ANSWER
x < 2, y > x + 1
Daily
Homework
Quiz
Warm-Up
Exercises
2.
A bibliography can refer to at most 8 articles, at
most 4 books, and at most 8 references in all. Write
and graph a system of inequalities that models the
situation.
ANSWER
x = articles, y = books; x  8, y  4,
x + y  8, x  0, and y  0