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Ch. 1 - Equations and Inequalities
Lial - College Algebra 13th Edition
Lial13th EditionCollege AlgebraISBN: 9780136881063Not the one you use?Change textbook
Chapter 2, Problem 56

Solve each equation or inequality.
129x12| 12- 9x | ≥ -12

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1
Recognize that the absolute value expression \(|12 - 9x|\) represents the distance of the quantity \((12 - 9x)\) from zero on the number line, and absolute values are always non-negative (i.e., \(|a| \geq 0\) for any real number \(a\)).
Note that the inequality is \(|12 - 9x| \geq -12\). Since the right side is a negative number, and absolute values are always greater than or equal to zero, this inequality will always be true for all real values of \(x\).
Formally, because \(|12 - 9x| \geq 0\) and \(0 \geq -12\), the inequality \(|12 - 9x| \geq -12\) holds for every real number \(x\).
Therefore, the solution set is all real numbers, which can be written as \((-\infty, \infty)\).
To summarize, no further algebraic manipulation is needed because the inequality is always true due to the properties of absolute value.

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Key Concepts

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

Absolute Value Inequalities

Absolute value inequalities involve expressions where the absolute value of a variable or expression is compared to a number. Since absolute value represents distance from zero, it is always non-negative, which affects how inequalities are solved and interpreted.
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Properties of Absolute Value

The absolute value of a number is its distance from zero on the number line, always non-negative. For any real number x, |x| ≥ 0, and |x| = a implies x = a or x = -a. This property helps in breaking down absolute value inequalities into separate cases.
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Solving Linear Inequalities

Solving linear inequalities involves isolating the variable and considering the direction of the inequality. When multiplying or dividing by a negative number, the inequality sign reverses. Understanding this is essential when solving inequalities derived from absolute value expressions.
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