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Ch. R - Review of Basic Concepts
Lial - College Algebra 13th Edition
Lial13th EditionCollege AlgebraISBN: 9780136881063Not the one you use?Change textbook
Chapter 1, Problem 17

Determine whether each statement is true or false. |25| = |-25|

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Recall the definition of absolute value: for any real number \(x\), \(|x|\) represents the distance of \(x\) from zero on the number line, which is always non-negative.
Evaluate the absolute value of 25: \(|25|\) is the distance of 25 from zero, which is simply 25.
Evaluate the absolute value of -25: \(|-25|\) is the distance of -25 from zero, which is also 25 because distance is always positive.
Compare the two values: since both \(|25|\) and \(|-25|\) equal 25, they are equal.
Conclude that the statement \(|25| = |-25|\) is true because absolute value ignores the sign of the number.

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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 is its distance from zero on the number line, always expressed as a non-negative value. For any real number x, |x| equals x if x is positive or zero, and -x if x is negative.
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Properties of Absolute Value

Absolute value has key properties such as |a| ≥ 0 for any real number a, and |a| = |-a|, meaning the absolute value of a number is equal to the absolute value of its opposite. This property is essential for comparing expressions involving absolute values.
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Evaluating Absolute Value Expressions

To evaluate an absolute value expression, substitute the number inside the bars and apply the definition. For example, |25| = 25 because 25 is positive, and |-25| = 25 because the negative sign is negated by the absolute value.
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