Tuesday, January 26, 2010

A first cut at negative quantities

One can subtract directly, as we did in the last posting, e.g.

my littlest son's weight today Tuesday - his weight at birth on Thursday = 4 oz.

Sometimes, however, such subtractions result in a negative answer, e.g.

his weight at his first doctor's visit on Friday - his weight at birth on Thursday = -4 oz.

The most familiar way to represent negative quantities is as the opposite, or negative, of a positive quantity.  This is convenient for many purposes, but it is not the only way, or even the most convenient, as we shall see.

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