       Re: modulo solving lacking domain?

• To: mathgroup at smc.vnet.net
• Subject: [mg126844] Re: modulo solving lacking domain?
• From: Dana DeLouis <dana01 at me.com>
• Date: Wed, 13 Jun 2012 04:54:11 -0400 (EDT)
• Delivered-to: l-mathgroup@mail-archive0.wolfram.com

```> Solve[12*n==8,n,Modulus->20]
> {{n->4+5*C}}
>
> It omits C element of Integers.

Hi.  Don't know where one would find this, so try:

Solve[12*n==8,n,Integers,Modulus->20]

Solve::mdom: Warning: Mathematica is ignoring domain specification Integers;
option setting Modulus -> 20 implies domain integers modulo 20.

There you go!
..  Modulus -> 20 implies domain integers   :>)

//  And the solution appears to check ok.

Table[Mod[12(4+5 c), 20], {c, -3, 10}]
{8,8,8,8,8,8,8,8,8,8,8,8,8,8}

= = = = = = = = = =
HTH  :>)
Dana DeLouis
Mac & Math 8
= = = = = = = = = =

On Jun 12, 3:02 am, Richard Fateman <fate... at cs.berkeley.edu> wrote:
> Solve[12*n==8,n,Modulus->20]
>
> returns
> {{n->4+5*C}}
>
> It omits C element of Integers.
> I doubt that this is a feature; is it a bug?
>
> C is not necessarily a member of the finite field of
> integers modulo 20.  It is obvious not an arbitrary Real.

```

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