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Ch. 1 - Equations and Inequalities
Blitzer - College Algebra 8th Edition
Blitzer8th EditionCollege AlgebraISBN: 9780136970514Not the one you use?Change textbook
Chapter 2, Problem 85

In Exercises 59–94, solve each absolute value inequality. 3 ≤ |2x - 1|

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1
Recall that the absolute value inequality \(3 \leq |2x - 1|\) means the expression inside the absolute value, \$2x - 1$, is at least 3 units away from 0 on the number line.
Rewrite the inequality \(3 \leq |2x - 1|\) as two separate inequalities to remove the absolute value: \(2x - 1 \leq -3\) or \(2x - 1 \geq 3\).
Solve the first inequality \(2x - 1 \leq -3\) by adding 1 to both sides: \(2x \leq -2\), then divide both sides by 2 to get \(x \leq -1\).
Solve the second inequality \(2x - 1 \geq 3\) by adding 1 to both sides: \(2x \geq 4\), then divide both sides by 2 to get \(x \geq 2\).
Combine the two solution sets to express the final answer: \(x \leq -1\) or \(x \geq 2\).

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Absolute Value Definition

The absolute value of a number represents its distance from zero on the number line, always as a non-negative value. For an expression |A|, it equals A if A ≥ 0, and -A if A < 0. Understanding this helps in rewriting absolute value inequalities into equivalent compound inequalities.
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Solving Absolute Value Inequalities

To solve inequalities involving absolute values, such as |A| ≥ k, where k ≥ 0, split the inequality into two cases: A ≥ k or A ≤ -k. This approach transforms the absolute value inequality into two linear inequalities that can be solved separately.
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Compound Inequalities and Solution Sets

After splitting the absolute value inequality, the solution is the union of the solution sets of the two inequalities. Understanding how to combine these sets correctly is essential to express the final answer, often in interval notation, representing all values satisfying the original inequality.
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