Solve the Absolute Value Inequality: |2x - 4| < 8

Absolute Value Inequalities with Compound Solutions

Given:

2x4<8 \left|2x-4\right|<8

Which of the following statements is necessarily true?

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1

Understand the problem

Given:

2x4<8 \left|2x-4\right|<8

Which of the following statements is necessarily true?

2

Step-by-step solution

To solve the absolute value inequality 2x4<8 |2x - 4| < 8 , we begin by removing the absolute value expression. This gives us a compound inequality:

8<2x4<8-8 < 2x - 4 < 8.

We will solve this compound inequality by handling each part separately:

  • Start with the left inequality: 8<2x4-8 < 2x - 4.
    • Add 4 to both sides to isolate the term with x x : 8+4<2x-8 + 4 < 2x.
    • Simplify: 4<2x-4 < 2x.
    • Finally, divide both sides by 2: 2<x-2 < x.
  • Now, solve the right inequality: 2x4<82x - 4 < 8.
    • Add 4 to both sides to isolate the term with x x : 2x4+4<8+42x - 4 + 4 < 8 + 4.
    • Simplify: 2x<122x < 12.
    • Finally, divide both sides by 2: x<6x < 6.

Combining the two solutions from the parts, we find:

2<x<6-2 < x < 6.

The solution indicates that x x must be greater than -2 and less than 6. This form matches answer choice 4. Therefore, the correct solution is:

2<x<6-2 < x < 6.

3

Final Answer

2<x<6 -2 < x < 6

Key Points to Remember

Essential concepts to master this topic
  • Rule: |expression| < number creates compound inequality: -number < expression < number
  • Technique: Solve both parts separately: -8 < 2x - 4 and 2x - 4 < 8
  • Check: Test boundary values: x = -1.9 gives |2(-1.9) - 4| = 7.8 < 8 ✓

Common Mistakes

Avoid these frequent errors
  • Solving as two separate inequalities instead of compound
    Don't split |2x - 4| < 8 into 2x - 4 < 8 OR 2x - 4 > -8 = wrong solution set! This gives you the union instead of intersection. Always write as compound: -8 < 2x - 4 < 8.

Practice Quiz

Test your knowledge with interactive questions

Given:

\( \left|2x-1\right|>-10 \)

Which of the following statements is necessarily true?

FAQ

Everything you need to know about this question

Why does the absolute value inequality become a compound inequality?

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The absolute value 2x4 |2x - 4| measures distance from zero. When this distance is less than 8, the expression inside must be between -8 and 8, creating the compound inequality.

How do I know when to use 'and' versus 'or' with absolute values?

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Use 'and' (compound) when the inequality is less than (<). Use 'or' (union) when the inequality is greater than (>). Think: less than means 'between' values.

What if I get confused about which direction the inequality signs go?

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Remember: expression<number |expression| < number means the expression is trapped between -number and +number. So write: number<expression<+number -number < expression < +number .

How can I check if my final answer makes sense?

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Pick any value from your solution interval and substitute it back. For 2<x<6 -2 < x < 6 , try x = 0: 2(0)4=4<8 |2(0) - 4| = 4 < 8

What's the difference between < and ≤ in absolute value inequalities?

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The symbol determines whether boundary points are included. With <, the endpoints -2 and 6 are not part of the solution. With ≤, they would be included.

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