equation



-----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
??