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Re: Why this cannot be solved

  • To: mathgroup at smc.vnet.net
  • Subject: [mg116248] Re: Why this cannot be solved
  • From: olfa <olfa.mraihi at yahoo.fr>
  • Date: Tue, 8 Feb 2011 05:06:40 -0500 (EST)
  • References: <iie085$bpp$1@smc.vnet.net> <iig77c$rle$1@smc.vnet.net>

On 4 f=E9v, 07:43, "Sjoerd C. de Vries" <sjoerd.c.devr... at gmail.com>
wrote:
> I'm not sure what you're trying to do here, aP is a function name, not
> a variable. You can't solve for that. Also aP == a is not an algebrai=
c
> equation as both aP and a are heads not variables.
>
> Cheers -- Sjoerd
>
>  On Feb 3, 11:32 am, olfa <olfa.mra... at yahoo.fr> wrote:
>
>
>
> > Hi Mathematica community,
> > System 1)
> > Reduce[Max[e, s + a[i]] == Max[c, d + aP[iP]] && d == s - a[n]
> > +Sum[a[j],{j,i,n}] &&
> >    aP == a && iP == n, {aP, iP, d, c}, Reals]
>
> > this gives:
> > Reduce::nsmet: This system cannot be solved with the methods available
> > to Reduce.
>
> > System 2)
> > Reduce[Max[e, s + a[i]] == Max[c, d + aP[iP]] && d == s - a[n]
> > +Sum[a[j],{j,i,n}] , { d, c}, Reals]
>
> > this gives solutions.
>
> > the only difference between them is the variables aP and iP and their
> > respective equations.
> > What I didn't understand is why the first system cannot be solved
> > although I have given values for iP and aP inside of it?
>
> > thank you.- Masquer le texte des messages pr=E9c=E9dents -
>
> - Afficher le texte des messages pr=E9c=E9dents -

if aP == a is not an algebraic equation as both aP and a are heads not
variableshere why this example works:
Reduce[x + Sum[a[index], {index, k, n}] ==
   xP + Sum[aP[index], {index, kP, n}] && aP == a, {aP, xP},
 Backsubstitution -> True]?
Thank you.


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