Hi - Even if you try eliminate([f1,f2],[B]) or eliminate([f1,f2],[F]), you
get some very ugly expressions which seem to defy simplfication or solution.
Also eliminate([f1,f2],[B,F]) produces [0] as a result. So, this system may
defy symbolic solution (unfortunately), and a numerical method seems the
only recourse.
Dave Holmgren
> > I'm new to Maxima
>
> Thanks for your interest in Maxima!
>
> > f1: (Rb/Bmin) * B * (B - Bmin) * (1 - B/Bmax) - A * B * F = 0;
> > f2: (Rf/Fmin) * F * (F - Fmin) * (1 - F/Fmax) - A * B * F = 0;
> > res: solve ([f1, f2], [B, F]);
> >
> > Now if I input just that, and try to solve it symbolically,
> > Maxima hangs.
>
> I think you have found a bug.
>
> Your system reduces to something of the form:
>
> q1: b2 * B^2 + b1 * B + b0 + bf * F = 0
>
> q2: f2 * F^2 + f1 * F + f0 + fb * B = 0
>
> and Maxima seems to run forever on that, too.
>
> I tried solving the system step by step.
>
> First, I solved for F in f1 and substituted. This leads to a quartic
> mess.
>
> Then I tried solving for B in f1 and substituting into f2; Solve solves
> the resulting equation easily. There are two non-trivial solutions in
> each step, and you'll have to check which ones are meaningful.
>
> By the way, it can be helpful to declare some facts about your
> parameters, e.g.
>
> assume(Bmax>B,B>Bmin,Bmin>0,
> Fmax>F,F>Fmin,Fmin>0,
> Rb>0,Rf>0,A>0)
>
> This will keep some radicals "clean", though it does *not* use these
> facts in Solve (for example, you will get the B=0, F=0 solution).
>
> Good luck.
>
> -s
>
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