Solve |5x + 3| ≤ 7: Absolute Value Inequality Analysis

Absolute Value Inequalities with Compound Solutions

Given:

5x+37 \left|5x + 3\right| \leq 7

Which of the following statements is necessarily true?

❤️ Continue Your Math Journey!

We have hundreds of course questions with personalized recommendations + Account 100% premium

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

Given:

5x+37 \left|5x + 3\right| \leq 7

Which of the following statements is necessarily true?

2

Step-by-step solution

To solve 5x+37 \left| 5x + 3 \right| \leq 7 , consider both cases:5x+37 5x + 3 \leq 7 and 5x+37 5x + 3 \geq -7 .

1. Solving 5x+37 5x + 3 \leq 7 :

5x+37 5x + 3 \leq 7

Subtract 3 from both sides:

5x4 5x \leq 4

Divide both sides by 5:

x0.8 x \leq 0.8

2. Solving 5x+37 5x + 3 \geq -7 :

5x+37 5x + 3 \geq -7

Subtract 3 from both sides:

5x10 5x \geq -10

Divide both sides by 5:

x2 x \geq -2

Combining both results, we find 2x0.8 -2 \leq x \leq 0.8 .

3

Final Answer

2x0.8 -2 \leq x \leq 0.8

Key Points to Remember

Essential concepts to master this topic
  • Rule: For |ax + b| ≤ c, create two inequalities: ax + b ≤ c and ax + b ≥ -c
  • Technique: Solve each inequality separately, then combine with 'and' for intersection
  • Check: Test boundary values x = -2 and x = 0.8 in original inequality ✓

Common Mistakes

Avoid these frequent errors
  • Using 'or' instead of 'and' to combine solutions
    Don't write x ≥ -2 OR x ≤ 0.8 = all real numbers! This means the absolute value is always true, which is wrong. Always use 'and' for ≤ inequalities: -2 ≤ x ≤ 0.8 creates the correct bounded 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 do I need both -7 and +7 in my inequalities?

+

The absolute value |5x + 3| represents distance from zero. For this distance to be ≤ 7, the expression inside must be between -7 and +7, giving you both boundary conditions.

How is this different from |5x + 3| ≥ 7?

+

With , you'd use 'or' to combine solutions because you want values outside the interval. With , you use 'and' because you want values inside the interval.

Can I solve this by removing the absolute value bars directly?

+

No! You can't just delete the bars. The absolute value creates two cases that must both be satisfied simultaneously for ≤ inequalities.

What if I get fractions or decimals in my answer?

+

That's perfectly normal! Convert fractions to decimals for easier comparison: 45=0.8 \frac{4}{5} = 0.8 . Your final answer can use either form.

How do I check if x = 0 works in this problem?

+

Substitute: 5(0)+3=3=3 |5(0) + 3| = |3| = 3 . Since 3 ≤ 7 is true, x = 0 is indeed in our solution interval [-2, 0.8].

🌟 Unlock Your Math Potential

Get unlimited access to all 18 Absolute Value and Inequality questions, detailed video solutions, and personalized progress tracking.

📹

Unlimited Video Solutions

Step-by-step explanations for every problem

📊

Progress Analytics

Track your mastery across all topics

🚫

Ad-Free Learning

Focus on math without distractions

No credit card required • Cancel anytime

More Questions

Click on any question to see the complete solution with step-by-step explanations