Solve |4x+12| > 16: Absolute Value Inequality Challenge

Absolute Value Inequalities with Union Solutions

Given:

4x+12>16 \left|4x+12\right|>16

Which of the following statements is necessarily true?

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1

Understand the problem

Given:

4x+12>16 \left|4x+12\right|>16

Which of the following statements is necessarily true?

2

Step-by-step solution

To solve this inequality, we use the principle that if A>B |A| > B , then A>B A > B or A<B A < -B . Here's a detailed step-by-step solution:

  • Set up the two inequalities from the absolute value expression:
    1. 4x+12>16 4x + 12 > 16
    2. 4x+12<16 4x + 12 < -16
  • For the first inequality, 4x+12>16 4x + 12 > 16 :
    - Subtract 12 from both sides to isolate the term with x x :
    4x>1612 4x > 16 - 12
    4x>4 4x > 4
    - Divide both sides by 4:
    x>1 x > 1
  • For the second inequality, 4x+12<16 4x + 12 < -16 :
    - Subtract 12 from both sides:
    4x<1612 4x < -16 - 12
    4x<28 4x < -28
    - Divide both sides by 4:
    x<7 x < -7
  • The solution is the union of both results:
    x>1 x > 1 or x<7 x < -7

Therefore, the correct answer among the given choices is x>1 x > 1 or x<7 x < -7 .

3

Final Answer

x>1 x>1 or x<7 x<-7

Key Points to Remember

Essential concepts to master this topic
  • Rule: If |A| > B, then A > B or A < -B
  • Technique: Solve 4x + 12 > 16 and 4x + 12 < -16 separately
  • Check: Test x = 2: |4(2) + 12| = |20| = 20 > 16 ✓

Common Mistakes

Avoid these frequent errors
  • Using 'and' instead of 'or' to connect solutions
    Don't write x > 1 AND x < -7 = impossible condition! No number can be both greater than 1 and less than -7 simultaneously. Always use OR to connect the two solution regions for absolute value inequalities.

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 we get two separate inequalities from one absolute value inequality?

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The absolute value 4x+12 |4x+12| represents distance from zero. For this distance to be greater than 16, the expression inside can be either very positive (> 16) or very negative (< -16).

How do I know when to use 'or' versus 'and' in my final answer?

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For absolute value inequalities like A>B |A| > B , always use OR because we want values that satisfy either condition. Use 'and' only when both conditions must be true simultaneously.

What does the solution x > 1 or x < -7 look like on a number line?

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Draw two separate regions: everything to the right of 1 (not including 1) and everything to the left of -7 (not including -7). The middle section from -7 to 1 is not part of the solution.

Why isn't x = 1 or x = -7 included in the solution?

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Because our inequality uses > (greater than), not ≥. At x = 1: 4(1)+12=16 |4(1)+12| = 16 , which equals 16 but doesn't satisfy > 16.

How can I check if my solution regions are correct?

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  • Pick a test point from each region (like x = 2 and x = -8)
  • Substitute into the original inequality
  • Both should make 4x+12>16 |4x+12| > 16 true
  • Pick a point between the regions (like x = 0) - it should make the inequality false

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