If the ultimate goal is a decimal approximation, a purely floating point method is often better than symbolic solution followed by a conversion
to floating point. Try:
(%i102) allroots(-2*q^3+3*q-1.357008100494576);
(%o102) [q=0.58757180617091,q=0.82024709886951,q=-1.40781890504042]
(%i104) bfallroots(-2*q^3+3*q-1.357008100494576), fpprec : 28;
(%o104) [q=5.875718061709101990263852045b-1,q=8.202470988695097658442859279b-1,q=-1.407818905040419964870671132b0]
--Barton
________________________________________
From: maxima-bounces at math.utexas.edu [maxima-bounces at math.utexas.edu] on behalf of Thomas D. Dean [tomdean at speakeasy.org]
Sent: Friday, August 16, 2013 10:41
To: maxima at math.utexas.edu
Subject: Re: [Maxima] 3rd order equations
On 08/16/13 05:56, Esben Byskov wrote:
> *Maybe somebody can help.
>
> I have tried to solve the following rather simple equation using maxima:
>
> (%i1) Eq: -2*q^3+3*q-1.357008100494576;
> (%o1) - 2 q + 3 q - 1.357008100494576
>
Eq: -2*q^3+3*q-1357008100494576/1000000000000000;
load(to_poly_solve)$
to_poly_solve(Eq,q);
Tom Dean
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