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9-12 Extra Support Materials for Algebra 1 Unit 4 Lesson 9

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Extra Support Materials for Algebra 1

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Lesson 9

9.1 Warm-up 9.2 Activity 9.3 Activity

Unit 4, Lesson 9

Testing Points to Solve Inequalities

Extra Support Materials for Algebra 1

9.1

Warm-up

Solve the inequality and use a test point to check your answer.

Step 1:

The equation negative 4x equals 12 being solved for x.

Step 2:

When .

, so 0 is not a solution.

Step 3:

, so all solutions are .

9.2

Activity

Andre is working on . He figured out that when . He tested all these points:

When
When
When
When

Based on these results, Andre decides that solutions for should include -1 and 0, but not 2 or 3.

Andre is frustrated with how much computation he had to do. What advice would you give him about how many numbers to test and which ones to test?
Mai was trying to solve . She saw that when , . She reasoned, “Because the problem has a greater than sign, I wrote .” Mai skipped the step of testing points, and that led to an error.
1. Help Mai test points to figure out the correct solution to the inequality.
2. Explain to Mai what went wrong with her reasoning.

9.3

Activity

Each of these solutions has something wrong. Circle the place that is wrong and write a correction.

None