Date: Sep 20, 1999 3:58 AM
Author: Jon Haugsand
Subject: Re: -1 x -1 ?



* Guillermo Phillips
> Hello All,
>
> Here's something I've always wondered (perhaps in my naivety). Why
> should -1 x -1 = 1?
> I appreciate that lots of nice things come from this, but what's the
> fundamental reason for it?


Suppose you're a student with no money. However, your old folks are
willing to lend you 500$ a month for living. When you borrow 500$ and
use them, you actually have -500$. Suppose this have been going on for
a while, say ten months, so today your asset is -5000$. How "rich" are
you three months from now? That is: -5000$ + -500$ * 3 = -6500$. OK,
how "rich" were you 4 months ago?
That is: -5000$ + -500$ * -4 = -5000$ + 2000$ = 3000$.

--
Jon Haugsand
Norwegian Computing Center,
<mailto://haugsand@nr.no> Pho: +47 22852608 / +47 22852500,
Fax: +47 22697660, Pb 114 Blindern, N-0314 OSLO, Norway