Solve |b|-|12-3|+|5|<0: Multiple Absolute Value Inequality Challenge

Absolute Value Inequalities with Multiple Terms

Given:

b123+5<0 |b|-|12-3|+|5|<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:

b123+5<0 |b|-|12-3|+|5|<0

Which of the following statements is necessarily true?

2

Step-by-step solution

We have the inequality:

b123+5<0 |b|-|12-3|+|5|<0

First, evaluate the known absolute values:

  • 123=9 |12-3| = 9

  • 5=5 |5| = 5

Substitute these into the inequality:

b9+5<0 |b| - 9 + 5 < 0

Which simplifies to:

b4<0 |b| - 4 < 0

Adding 4 to both sides gives:

b<4 |b| < 4

The inequality b<4 |b| < 4 means that bb must be in the range:

4<b<4 -4 < b < 4

Thus, the correct choice for the solution is: 4<b<4 -4 < b < 4 .

3

Final Answer

4<b<4 -4 < b < 4

Key Points to Remember

Essential concepts to master this topic
  • Evaluation: Simplify known absolute values before solving the inequality
  • Technique: Transform |b| < 4 into -4 < b < 4
  • Check: Test b = 0: |0| - 9 + 5 = -4 < 0 ✓

Common Mistakes

Avoid these frequent errors
  • Forgetting to evaluate known absolute values first
    Don't leave |12-3| and |5| unevaluated = unnecessarily complex solving! This makes the problem much harder than needed. Always evaluate absolute values with known numbers first to simplify the inequality.

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 to evaluate |12-3| and |5| first?

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These are known values that don't depend on the variable b. Evaluating them first simplifies your inequality from b123+5<0 |b|-|12-3|+|5|<0 to the much easier b4<0 |b|-4<0 .

How does |b| < 4 become -4 < b < 4?

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The absolute value inequality b<4 |b| < 4 means the distance from b to 0 is less than 4. This happens when b is between -4 and 4, so 4<b<4 -4 < b < 4 .

What if I got |b| > 4 instead?

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Then the solution would be b<4 b < -4 or b>4 b > 4 . But in this problem, we have b<4 |b| < 4 , which gives us the interval between -4 and 4.

How can I check my answer?

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Pick any value in your solution range, like b = 0. Substitute: 0123+5=09+5=4<0 |0|-|12-3|+|5| = 0-9+5 = -4 < 0 ✓. Try a value outside the range like b = 5: 59+5=1>0 |5|-9+5 = 1 > 0 , which doesn't satisfy the inequality.

Why can't the answer be b > -2 or one of the other choices?

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Those ranges are either too wide or don't match our solution b<4 |b| < 4 . For example, if 10<b<10 -10 < b < 10 were correct, then b = 5 should work, but 54=1>0 |5|-4 = 1 > 0 , not < 0.

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