1. Solving Inequalities by Adding or Subtracting
3-2
Solving Inequalities by
Adding or Subtracting
Holt Algebra 1
Warm Up
Lesson Presentation
Lesson Quiz

2. Warm Up Graph each inequality. Write an inequality for each situation.
1. The temperature must be at least –10°F.
2. The temperature must be no more than 90°F.
–10 10
x ≥ –10
x ≤ 90
–90 90
Solve each equation.
3. x – 4 = 10 14
4. 15 = x + 1.1
13.9

3. Objectives Solve one-step inequalities by using addition.
Solve one-step inequalities by using subtraction.

5. Using Addition and Subtraction to Solve Inequalities
Solve the inequality and graph the solutions.
A. x + 12 < 20
–10 –8 –6 –4 –2 2 4 6 8 10
B. d – 5 > –7
–10 –8 –6 –4 –2 2 4 6 8 10

6. Since there can be an infinite number of solutions to an inequality, it is not possible to check all the solutions. You can check the endpoint and the direction of the inequality symbol.
The solutions of x + 9 < 15 are given by x < 6.

7. Application Problem
The Recommended Daily Allowance (RDA) of iron for a female in Sarah’s age group (14-18 years) is 15 mg per day. Sarah has consumed 11 mg of iron today. Write and solve an inequality to show how many more milligrams of iron Sarah can consume without exceeding RDA.

8. Sarah can consume ___ mg or less of iron without exceeding the RDA.
Amount taken
plus
15 mg
is at most
amount needed 11 + x  15
11 + x  15 1 2 3 4 5 6 7 8 9 10
Sarah can consume ___ mg or less of iron without exceeding the RDA.

9. Application Problem
What if…? Josh wants to try to break the school bench press record of 282 pounds. He currently can bench press 250 pounds. Write and solve an inequality to determine how many more pounds Josh needs to lift to break the school record.

10. Josh must lift more than ____ additional pounds to reach his goal.
is greater than
250 pounds
plus
additional pounds
282 pounds.
250 + p
>
282
250 + p
>
Josh must lift more than ____ additional pounds to reach his goal.

11. Lesson Quiz
1. A certain restaurant has room for 120 customers. On one night, there are 72 customers dining. Write and solve an inequality to show how many more people can eat at the restaurant.
x + 72 ≤ 120; x ≤ 48,
where x is a natural number

12. Homework
Pages :
1-15; 32-33
Due Thursday 10/22/09