Re: Big problem in solving radicals.
- To: mathgroup at smc.vnet.net
- Subject: [mg41761] Re: Big problem in solving radicals.
- From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
- Date: Wed, 4 Jun 2003 08:34:42 -0400 (EDT)
- Organization: Universitaet Leipzig
- References: <bbi16p$7c1$1@smc.vnet.net>
- Reply-to: kuska at informatik.uni-leipzig.de
- Sender: owner-wri-mathgroup at wolfram.com
Hi,
{{x -> a^2}}
*is* the general solution, nobody say that x (or a)
must be real.
There is no way to ask Mathematica for only a real
solution in symbolic expressions.
Regards
Jens
Davide Del Vento wrote:
>
> Consider the following equation
>
> 1/2
> x + a = 0
>
> If you try to solve it with "Solve" you get
>
> 2
> x = a
>
> Of course, you know, this is not a general solution, e.g. if a>0 there
> isn't any (real) solution, and the complex solution is NOT the one
> printed by Mathematica.
>
> In the case of this example the problem is obvious and one can track
> it by hand, but what's about bigger equations with many solutions?
> Mathematica claims that "Solve" makes special assumptions about the
> parameters in the equation, so I was ready to such behaviour. I tested "Reduce"
> that should solve equation, giving explicitely the range of the
> parameters where the solutions are defined. Unfortunately it doesn't
> work right too.
>
> ;Davide Del Vento
>
> CNR Istituto Fisica Spazio Interplanetario
> via del Fosso del Cavaliere, 100 / IT-00133 / Rome
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> E-Mail: davide @ astromeccanica.it
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