Maxima normally gives exact symbolic solutions.
To get the real roots of a polynomial, try
float(realroots(-x^3+x+0.25) ) -- the 'float' is necessary for obscure
historical reasons (sorry!).
To get all the roots (real and complex) of a polynomial, try
allroots(-x^3+x+0.25). Even if the roots are exactly real, allroots
sometimes returns a tiny imaginary part.
Check the documentation for more options (specifying precision etc.):
? realroots
? allroots
Welcome to Maxima!
-s
On Wed, Oct 13, 2010 at 15:16, egc <cooch17 at verizon.net> wrote:
> After 15+ years of using Maple, I've decided to take latest build of Maxima
> for a spin (motivated to some degree by the desire to find a symbolic
> algebra program I can have my students use at no cost). I've done a a bit of
> 'fooling' with Maxima (learn by doing), and am stuck on something which
> seems pretty trivial.
>
> Consider f : -x^3+x+0.25=0
>
> Now, I know from Maple that the roots of this polynomial are -0.83757,
> -0.26959, and 1.1072. However, in Maxima, if I try
>
> solve(f,x);
>
> I get something is is bizarrely large and convoluted -- all sorts of
> fractions, and square roots, and the like. I tried toggling different levels
> of float, but I still don't end up with a nice simple solution vector
> containing these three solutions.
>
> Pointers to the obvious solution? Thanks in advance (remember, newbie, more
> or less, so set phasers to 'singe only'). ;-)? I'll leave my implicit
> differentiation question to a followup post. ;-)
>
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