Question

Difficulty: MediumLinear Inequalities and Absolute Value

If xx satisfies the inequality 32x>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 32x>9|3 - 2x| > 9 splits into 32x>93 - 2x > 9 or 32x<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.
32x>93 - 2x > 9 or 32x<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: 32x>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: 32x<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
Rate this question