Solve the Absolute Value Inequality: |5x - 2| < 3x + 8

Absolute Value Inequalities with Linear Expressions

Given:

5x2<3x+8 \left|5x - 2\right| < 3x + 8

Which of the following statements is necessarily true?

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Step-by-step written solution

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1

Understand the problem

Given:

5x2<3x+8 \left|5x - 2\right| < 3x + 8

Which of the following statements is necessarily true?

2

Step-by-step solution

We start with the inequality: 5x2<3x+8 \left|5x - 2\right| < 3x + 8

This absolute value inequality breaks into two separate inequalities:

  • 5x2<3x+8 5x - 2 < 3x + 8

  • 5x2>(3x+8) 5x - 2 > -(3x + 8)

Solving the first inequality: 5x2<3x+8 5x - 2 < 3x + 8

  • Subtract 3x 3x from both sides: 2x2<8 2x - 2 < 8

  • Add 2 2 to both sides: 2x<10 2x < 10

  • Divide by 2 2 : x<5 x < 5

Solving the second inequality: 5x2>(3x+8) 5x - 2 > -(3x + 8)

  • Distribute the negative: 5x2>3x8 5x - 2 > -3x - 8

  • Add 3x 3x to both sides: 8x2>8 8x - 2 > -8

  • Add 2 2 to both sides: 8x>6 8x > -6

  • Divide by 8 8 : x>34 x > -\frac{3}{4}

The solution is the intersection: x<5 x < 5 and x>34 x > -\frac{3}{4} . Hence, 34<x<5 -\frac{3}{4} < x < 5 .

3

Final Answer

34<x<5 -\frac{3}{4} < x < 5

Key Points to Remember

Essential concepts to master this topic
  • Definition: |A| < B means -B < A < B when B > 0
  • Method: Split into two inequalities: 5x - 2 < 3x + 8 and 5x - 2 > -(3x + 8)
  • Check: Test x = 0: |5(0) - 2| = 2 < 3(0) + 8 = 8 ✓

Common Mistakes

Avoid these frequent errors
  • Forgetting to check if the right side is positive
    Don't assume 3x + 8 > 0 for all x values = invalid solutions! When 3x + 8 ≤ 0, the absolute value inequality has no solution since |expression| ≥ 0 always. Always verify 3x + 8 > 0 first, which gives x > -8/3.

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 do I need two separate inequalities?

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The absolute value 5x2 |5x - 2| represents distance from zero. This distance can come from positive or negative values, so we need both cases: when 5x - 2 is positive and when it's negative.

How do I handle the negative sign in the second inequality?

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When you have 5x2>(3x+8) 5x - 2 > -(3x + 8) , distribute the negative first: 5x2>3x8 5x - 2 > -3x - 8 . Then solve normally by collecting like terms.

What does the intersection of solutions mean?

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You need both conditions to be true simultaneously. From x<5 x < 5 AND x>34 x > -\frac{3}{4} , the overlap gives us 34<x<5 -\frac{3}{4} < x < 5 .

Can absolute value inequalities have no solution?

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Yes! If the right side becomes negative or zero, like x<2 |x| < -2 , there's no solution because absolute values are always non-negative.

How do I verify my answer range?

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Pick a test value from your solution interval, like x=0 x = 0 . Substitute: 5(0)2=2 |5(0) - 2| = 2 and 3(0)+8=8 3(0) + 8 = 8 . Since 2 < 8, our solution works!

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