Search All of the Math Forum:

Views expressed in these public forums are not endorsed by NCTM or The Math Forum.

Topic: -1 x -1 ?
Replies: 29   Last Post: May 13, 2009 9:01 AM

 Messages: [ Previous | Next ]
 Jon Haugsand Posts: 26 Registered: 12/12/04
Re: -1 x -1 ?
Posted: Sep 20, 1999 3:58 AM

* 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

Date Subject Author
9/16/99 Guillermo Phillips
9/16/99 Ian A. Mason
9/16/99 Peter Percival
9/16/99 Dave Seaman
9/17/99 Steve Leibel
9/17/99 Dale Henderson
9/18/99 Peter Percival
9/18/99 Bill Taylor
9/18/99 John Savard
9/19/99 carel
9/20/99 Jon Haugsand
9/20/99 HH
9/20/99 Jon Haugsand
9/20/99 Jonathan Hoyle
9/20/99 Jim Hunter
1/21/09 Tay
1/21/09 mensanator
1/21/09 lwalke3@lausd.net
1/22/09 Henry
1/22/09 David R Tribble
1/22/09 Dave L. Renfro
1/22/09 mensanator
5/12/09 Kayama
5/12/09 mensanator
5/12/09 hagman
5/12/09 Bill Dubuque
5/12/09 Bill Taylor
5/13/09 Cobra
5/13/09 Cobra