Question

Difficulty: MediumLinear Inequalities and Absolute Value

If xx satisfies the inequality ∣3−2x∣>9|3 - 2x| > 9, which of the following could be the value of xx? Select all that apply.

  1. −5-5Answer
  2. B
    −3-3
  3. C
    00
  4. D
    44
  5. 88Answer

Answer

The values −5-5 and 88 satisfy the inequality.
The absolute value inequality ∣3−2x∣>9|3 - 2x| > 9 splits into 3−2x>93 - 2x > 9 or 3−2x<−93 - 2x < -9. Solving these yields x<−3x < -3 or x>6x > 6. The value −5-5 is less than −3-3 and the value 88 is greater than 66, so both are valid solutions.

Step-by-Step Solution

1
Set up the two separate linear inequalities based on the definition of absolute value.
3−2x>93 - 2x > 9 or 3−2x<−93 - 2x < -9
An absolute value expression ∣u∣>c|u| > c (where c>0c > 0) breaks into two disjoint cases: u>cu > c or u<−cu < -c.
2
Solve the first case: 3−2x>93 - 2x > 9.
−2x>6  ⟹  x<−3-2x > 6 \implies x < -3
Subtract 3 from both sides to get −2x>6-2x > 6, then divide by −2-2 and reverse the inequality sign.
3
Solve the second case: 3−2x<−93 - 2x < -9.
−2x<−12  ⟹  x>6-2x < -12 \implies x > 6
Subtract 3 from both sides to get −2x<−12-2x < -12, then divide by −2-2 and reverse the inequality sign.
4
Combine the solution sets and evaluate the given options.
The valid solution set is x<−3x < -3 or x>6x > 6. Among the choices, −5-5 (since −5<−3-5 < -3) and 88 (since 8>68 > 6) fall into the solution set.
Values between −3-3 and 66, inclusive, do not satisfy the original inequality.

Key Concept

Solving absolute value inequalities of the form ∣u∣>c|u| > c by splitting into compound inequalities and reversing the direction of inequality signs when dividing by negative numbers.
Estimated Time:1m 15s
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