subtraction

subtraction, fundamental operation of arithmetic; the inverse of addition. If a and b are real numbers (see number), then the number a-b is that number (called the difference) which when added to b (the subtractor) equals a (the subtrahend). In terms of addition the symbol -b is called the additive inverse of b with the property that the sum of a number and its inverse equals 0, or b+(-b)=0. It follows that -(-b)=b. The subtraction of b from a is the same as the addition of a and the inverse of b, or a-b=a+(-b); e.g., when a=10 and b=5, then 10-5=10+(-5).

The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2007, Columbia University Press. All rights reserved.

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