carel
Posts:
161
Registered:
12/12/04
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Re: -1 x -1 ?
Posted:
Sep 19, 1999 12:01 AM
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John Savard wrote in message <37e3ccff.1687863@news.prosurfr.com>...
>"Guillermo Phillips" <Guillermo.Phillips@marsman.demon.co.uk> wrote,
>in part:
>
>>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?
>
>Well, negative numbers are kind of strange, almost like imaginary
>numbers. You have an empty box, and you can leave it empty, or you can
>put one pebble in it, or you can put two pebbles in it, and so on.
>
>But negative numbers can make sense for things like temperature and
>bank accounts.
>
>If you owe five dollars, that can be considered a way of having -5
>dollars.
>
>If you owe three people five dollars, you have 3 * -5 dollars, or -15
>dollars.
>
>If three people owe you five dollars, then you have an asset that is
>(hopefully, if they're honest) worth 15 dollars. So that's -3 * -5,
>the minus on the 3 standing for the fact that the debt is "the other
>way around".
>
>John Savard ( teneerf<- )
>http://www.ecn.ab.ca/~jsavard/crypto.htm
Or how about the following
-1 x 0 = 0
-1 x (1-1) = 0
(-1 x 1) + (-1 x -1 ) = 0
-1 + (-1 x -1) = 0
-1 + 1 + (-1 x -1) = 1
0 + (-1 x -1 ) = 1
-1 x -1 = 1
Carel
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