Solve: |-9 + |d + 7| + |-3d - 2|| < 0 - Complex Absolute Value Inequality

Absolute Value Inequalities with Impossible Solutions

Given:

9+d+7+3d2<0 |-9 + |d + 7| + |-3d - 2|| < 0

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:

9+d+7+3d2<0 |-9 + |d + 7| + |-3d - 2|| < 0

Which of the following statements is necessarily true?

2

Step-by-step solution

The given inequality is: 9+d+7+3d2<0 |-9 + |d + 7| + |-3d - 2| < 0 .

Both expressions, d+70|d + 7| \ge 0 and 3d20|-3d - 2| \ge 0, because absolute values cannot be negative.

Adding these with -9, the expression 9+d+7+3d2-9 + |d + 7| + |-3d - 2| will be greater than or equal to -9.

Since -9 is not less than 0, the inequality <0< 0 cannot hold true.

Therefore, the statement "No solution" is the correct answer.

3

Final Answer

No solution

Key Points to Remember

Essential concepts to master this topic
  • Absolute Value Property: All absolute value expressions are always non-negative
  • Analysis Technique: Find minimum value: -9 + 0 + 0 = -9
  • Solution Check: If minimum value ≥ 0, then no solution exists ✓

Common Mistakes

Avoid these frequent errors
  • Trying to solve by cases without analyzing the expression structure
    Don't immediately set up cases like |d + 7| = 0 and |-3d - 2| = 0 without first checking if the inequality can be satisfied! This wastes time on impossible equations. Always check if the left side can actually be less than the right side by finding the minimum possible value.

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 can't this inequality have any solutions?

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Because absolute values are always ≥ 0! The smallest possible values are d+7=0|d + 7| = 0 and 3d2=0|-3d - 2| = 0, making the minimum of the entire expression -9 + 0 + 0 = -9. Since -9 is not less than 0, the inequality is impossible.

How do I find the minimum value of an absolute value expression?

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Set each absolute value to zero (their smallest possible value). For 9+d+7+3d2-9 + |d + 7| + |-3d - 2|, the minimum is when both absolute values equal 0, giving us -9 + 0 + 0 = -9.

What if the inequality was > 0 instead of < 0?

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Then we'd have solutions! Since the minimum value is -9, the expression can be greater than 0. We'd need to find when 9+d+7+3d2>0-9 + |d + 7| + |-3d - 2| > 0, or when d+7+3d2>9|d + 7| + |-3d - 2| > 9.

Should I always check if an inequality is possible before solving?

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Yes! For complex absolute value inequalities, first determine the range of possible values for the left side. If this range doesn't overlap with what the inequality requires, you've saved yourself lots of work!

Can absolute value inequalities ever equal negative numbers?

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Never! Individual absolute values like x|x| are always ≥ 0. However, expressions containing absolute values (like 9+x-9 + |x|) can be negative if the constant term is large enough.

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