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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 87

In Exercises 59–94, solve each absolute value inequality. 5 > |4 - x|

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1
Recall that the absolute value inequality \$5 > |4 - x|\( means the distance between \)4 - x$ and \(0\) is less than 5.
Rewrite the inequality without the absolute value as a compound inequality: \(-5 < 4 - x < 5\).
Solve the left part of the compound inequality: \(-5 < 4 - x\). Subtract 4 from both sides to get \(-9 < -x\), then multiply both sides by \(-1\) (remember to reverse the inequality) to get \(x < 9\).
Solve the right part of the compound inequality: \$4 - x < 5\(. Subtract 4 from both sides to get \)-x < 1\(, then multiply both sides by \)-1\( (reverse the inequality) to get \)x > -1$.
Combine the two inequalities to write the solution as \(-1 < x < 9\).

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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 any expression |A|, it equals A if A is non-negative, and -A if A is negative. Understanding this helps in rewriting absolute value inequalities into equivalent compound inequalities.
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Solving Absolute Value Inequalities

An inequality involving absolute value, such as |A| < b (where b > 0), can be rewritten as a compound inequality: -b < A < b. This allows solving for the variable by isolating it within these bounds. Recognizing this form is essential to find the solution set for the inequality.
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Compound Inequalities

Compound inequalities involve two inequalities joined by 'and' or 'or'. For absolute value inequalities like |4 - x| < 5, the solution is found by solving the compound inequality -5 < 4 - x < 5. Understanding how to manipulate and solve these inequalities is key to determining the correct solution range.
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