Example

Simplifying x−88−x\frac{x-8}{8-x}

Simplify x−88−x\frac{x - 8}{8 - x}.

The numerator x−8x - 8 and the denominator 8−x8 - x are opposites of each other, since 8−x=−(x−8)8 - x = -(x - 8). By the opposite factors property, an expression divided by its opposite equals −1-1:

x−88−x=−1\frac{x - 8}{8 - x} = -1

To see why, recognize that the denominator can be rewritten as 8−x=−1⋅(x−8)8 - x = -1 \cdot (x - 8). Substituting gives 1⋅(x−8)−1⋅(x−8)\frac{1 \cdot (x - 8)}{-1 \cdot (x - 8)}. The common factor (x−8)(x - 8) divides out, leaving 1−1=−1\frac{1}{-1} = -1. This example demonstrates a direct application of the property a−bb−a=−1\frac{a - b}{b - a} = -1: once the numerator and denominator are identified as opposites, the simplified result follows immediately.

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Updated 2026-04-21

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