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### Negative Times a Negative

```
Date: 01/12/97 at 17:31:21
From: Sue Whittaker
Subject: Negative times a negative

I am a student teacher who is having a hard time explaining why a
negative times a negative is positive.  Can you give an example?

Thanks, Sue Whittaker
```

```
Date: 01/12/97 at 21:39:35
From: Doctor Robert
Subject: Re: Negative times a negative

You can, of course, prove that a negative times a negative is a
positive using the field axioms.  But the best way to give a
plausibility argument is to look at multiplication patterns.

3 x -3 = -9
2 x -3 = -6
1 x -3 = -3
0 x -3 =  0
-1 x -3 =  3

Voila!

-Doctor Robert,  The Math Forum
Check out our web site!  http://mathforum.org/dr.math/
```
Associated Topics:
Middle School Negative Numbers

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