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Example

Evaluating −x-x for Given Values of xx

To evaluate the expression −x-x, substitute the given value for xx and then determine the opposite of that value.

When x=8x = 8: Replace xx with 88 to obtain −(8)-(8). The opposite of 88 is −8-8, so −x=−8-x = -8.

When x=−8x = -8: Replace xx with −8-8 to obtain −(−8)-(-8). The opposite of −8-8 is 88, so −x=8-x = 8.

This example illustrates a key point: without knowing whether a variable represents a positive or negative number, we cannot determine the sign of −x-x. If xx is positive, then −x-x is negative; if xx is negative, then −x-x is positive.

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Updated 2026-04-21

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