RE: Re: List of solution
- To: mathgroup at smc.vnet.net
- Subject: [mg47005] RE: [mg46990] Re: List of solution
- From: "Florian Jaccard" <florian.jaccard at eiaj.ch>
- Date: Sat, 20 Mar 2004 03:50:17 -0500 (EST)
- Reply-to: <florian.jaccard at eiaj.ch>
- Sender: owner-wri-mathgroup at wolfram.com
It is true...
But the Select[%, FreeQ[#, I] &] method doesn't do it better...
But you can use :
Reduce[x^3 - 10x + 1 == 0,x,Reals]
This shoes that the 3 solutions are Real...
So you can obtain the exact solutions like this :
Simplify[ComplexExpand //@ Solve[x^3 - 10x + 1 == 0, x]]
And if you want a automatic "real solve" function, you can for example make
this :
mySolveReal[equ_, var_] :=
DeleteCases[Simplify[
ComplexExpand //@ Solve[equ,
var]], {var -> xx_} /;
Im[xx] != 0]
and try on a few examples... It works fine on your example !
mySolveReal[x^3-10x+1==0,x]
mySolveReal[x^2-x-10==0,x]
mySolveReal[x^2-x+10==0,x]
Meilleures salutations
Florian Jaccard
-----Message d'origine-----
De : astanoff [mailto:astanoff at yahoo.fr]
Envoyé : ven., 19. mars 2004 07:36
À : mathgroup at smc.vnet.net
Objet : [mg46990] Re: List of solution
Florian Jaccard wrote:
> Hello !
> C'est très simple :
> In[4]:=
> liste = {{x -> 0, y -> 0}, {x -> 1, y -> 0},
> {x -> I, y -> 1 + 2*I}}
> Out[4]=
> {{x -> 0, y -> 0}, {x -> 1, y -> 0},
> {x -> I, y -> 1 + 2*I}}
> In[5]:=
> DeleteCases[liste, {x -> xx_, y -> yy_} /;
> Im[xx] != 0 || Im[yy] != 0]
> Out[5]=
> {{x -> 0, y -> 0}, {x -> 1, y -> 0}}
The case with 3 real roots Solve[x^3 - 10x + 1 == 0] doesn't seem to work
fine...
--
0% de pub! Que du bonheur et des vrais adhérents !
Vous aussi inscrivez-vous sans plus tarder!!
Message posté à partir de http://www.gyptis.org, BBS actif depuis 1995.