Barton,
thanks for help,
Leon
P.S.
In the attached file are solutions returned by Mathematica and DERIVE
Dnia 23-02-2011 o godz. 12:56 Barton Willis napisa?(a):
> -----maxima-bounces at math.utexas.edu wrote: -----
>
> >?????solve((abs(q)*abs(4*Q+(2^(3/2)+1)*q))/(8*%pi*a^2*abs(eps0)),Q)
> >
> >Is?the?above?eq.?to?hard??
>
> The optional package to_poly_solver has a function that will solve this
> equation:
>
> ?(%i1) load(to_poly_solver)$
> ??Loading maxima-grobner $Revision: 1.6 $ $Date: 2009/06/02 07:49:49 $
>
> ?(%i2) sol :
> %solve((abs(q)*abs(4*Q+(2^(3/2)+1)*q))/(8*%pi*a^2*abs(eps0)),Q)$
>
> The solution is lengthy and has (redundant) conditions on the
> parameters. Let's
> tell Maxima that eps0 # 0, q # 0 and re-simplify:
>
> ?(%i3) assume(notequal(eps0,0),notequal(q,0));
> ?(%o3) [notequal(eps0,0),notequal(q,0)]
>
> To re-simplify, use the (undocumented, I think) trick
> ?
> ?(%i4) expand(sol,0,0);
> ?(%o4) %union([Q=-((2^(3/2)+1)*q)/4])
>
> Your equation is equivalent to 4*Q+(2^(3/2)+1)*q = 0. Since this
> equation is linear in Q, all the
> conditionals in sol should simplify to true automatically, I think. We
> should alert the author of
> to_poly_solve (and that would be me).
>
>
> --Barton
> ??
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