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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
> Phone:  +390649934357
> Fax:    +390649934383
> Mobile: +393288329015
> E-Mail: davide @ astromeccanica.it
> E-Mail: del vento @ ifsi . rm . cnr . it


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