As Joey Tuttle observed yesterday, in J you have 
the option of switching into extended precision 
to get exact answers.  (Or, if the original numbers
are not rational, to get more exact answers.)

   A=:2 2 $ 1 1.0000001 1 1
   b=:2.0000001 2

   b %. A
0.911182 1.08882
   b %.&x: A
1 1



----- Original Message -----
From: John Randall <[email protected]>
Date: Monday, January 12, 2009 7:14
Subject: Re: [Jprogramming] Solving formulas
To: Programming forum <[email protected]>

> Henry Rich wrote:
> >     570 470 %. 2 2 $ 3 5 5 3
> > 40 90
> 
> This is a good method for well conditioned matrices. Results 
> need to be
> interpreted more carefully in cases like
> 
> A=:2 2 $ 1 1.0000001 1 1
> b=:2.0000001 2
> 
>    b %. A
> 0.911182 1.08882
>    b-:A +/ .* 1 1
> 1
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