Solve |3x - 4| ≤ 5: Absolute Value Inequality Solution

Absolute Value Inequalities with Compound Solutions

Given:

3x45 \left|3x - 4\right| \leq 5

Which of the following statements is necessarily true?

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Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

Given:

3x45 \left|3x - 4\right| \leq 5

Which of the following statements is necessarily true?

2

Step-by-step solution

To solve 3x45 \left| 3x - 4 \right| \leq 5 , we should consider two scenarios for the absolute value: 3x45 3x - 4 \leq 5 and 3x45 3x - 4 \geq -5 .

1. Solving 3x45 3x - 4 \leq 5 :

3x45 3x - 4 \leq 5

Add 4 to both sides:

3x9 3x \leq 9

Divide both sides by 3:

x3 x \leq 3

2. Solving 3x45 3x - 4 \geq -5 :

3x45 3x - 4 \geq -5

Add 4 to both sides:

3x1 3x \geq -1

Divide both sides by 3:

x13 x \geq -\frac{1}{3}

Combining both results, we have 13x3 -\frac{1}{3} \leq x \leq 3 , which is the correct answer.

3

Final Answer

13x3 -\frac{1}{3} \leq x \leq 3

Key Points to Remember

Essential concepts to master this topic
  • Rule: |expression| ≤ number creates two inequalities with AND
  • Technique: Rewrite |3x - 4| ≤ 5 as -5 ≤ 3x - 4 ≤ 5
  • Check: Test boundary values: x = -1/3 gives |3(-1/3) - 4| = |-5| = 5 ≤ 5 ✓

Common Mistakes

Avoid these frequent errors
  • Writing two separate OR conditions instead of AND
    Don't solve |3x - 4| ≤ 5 as 3x - 4 ≤ 5 OR 3x - 4 ≥ -5 = gives wrong union! This misunderstands absolute value inequalities. Always use AND to create the intersection: -5 ≤ 3x - 4 ≤ 5 for one solution interval.

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 ≤ create an AND condition instead of OR?

+

Think of absolute value as distance from zero. When 3x45 |3x - 4| \leq 5 , you're saying the distance is at most 5, which means the expression must be between -5 and 5. That's an AND condition!

How is this different from |3x - 4| ≥ 5?

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Great question! 3x45 |3x - 4| \geq 5 would give you OR conditions: either 3x45 3x - 4 \leq -5 OR 3x45 3x - 4 \geq 5 . The ≥ creates two separate regions!

Can I solve the two inequalities separately?

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Yes, but remember they must both be true simultaneously. Solve 3x45 3x - 4 \leq 5 to get x3 x \leq 3 , and solve 3x45 3x - 4 \geq -5 to get x13 x \geq -\frac{1}{3} . Then find where both are true!

How do I check if my interval is correct?

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Pick test values! Try x=0 x = 0 (inside your interval): 3(0)4=45 |3(0) - 4| = 4 \leq 5 ✓ . Try x=4 x = 4 (outside): 3(4)4=8>5 |3(4) - 4| = 8 > 5 ✗ .

What does the solution interval -1/3 ≤ x ≤ 3 mean visually?

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On a number line, it's all values between and including 13 -\frac{1}{3} and 3. Use closed circles at both endpoints since we have ≤ signs!

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