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Math Forum » Discussions » sci.math.* » sci.math.independent

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

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lwalke3@lausd.net

Posts: 2,394
Registered: 8/3/07
Re: -1 x -1 ?
Posted: Jan 21, 2009 10:31 PM
  Click to see the message monospaced in plain text Plain Text   Click to reply to this topic Reply

On Jan 21, 6:03 pm, Mensanator <mensana...@aol.com> wrote:
> On Jan 21, 7:51 pm, Tay <wintct...@gmail.com> wrote:
> > -1 *-1 = 1 huh?
> > Well, think of it like this:
> > The minus (negative) signs cancel eachother out:
> > (-1)(-1)=
> > [(-)(-)](1x1)=
> > So then, multiply the + and numbers
> > (+)(1x1)=
> > You've got positive 1:
> > +1
> > It's so simple.

On the other hand, Timothy Golden, the inventor of
polysigned numbers, thinks of it as:

- is the first sign.
+ is the second sign (and also the zeroth sign)

So to multiply two numbers, add their signs:

(-1)(-1) = (first-sign 1)(first-sign 1)
= second-sign 1
= +1.

> If North is positive and you're facing South,
> what's your displacement if you take a step backwards?

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