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Re: anything faster than Solve[] for solving sets of polynomial equations symbolically?

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  Re: anything faster than Solve[] for solving sets of polynomial equations symbolically? dantimatter <google@dantimatter.com> - 2011-05-10 00:22 +0000

#2254 — Re: anything faster than Solve[] for solving sets of polynomial equations symbolically?

Hi David,
I tried doing what you suggested, that is,  

> eqs = {-k5 x1 x3 + k6 x4 == 0,
>    k1 x1 - k4 x2 - 2 k2 x2^2 + 2 k3 x3 + k7 x4 == 0,
>    k2 x2^2 - k3 x3 - k5 x1 x3 + k6 x4 == 0, x1 + x4 - Xtot == 0};
>
> sol = Solve[eqs, {x1, x2, x3, x4}, Reals];
>
> solSimple =
>  Assuming[{k1 >= 0, k2 >= 0, k3 >= 0, k4 >= 0, k5 >= 0, k6 >= 0,
>    k7 >= 0, Xtot >= 0}, Simplify[sol]]
>

but when I take a look at one of the solutions, for example, solSimple[[2, 1]], the answer has both a real and imaginary component.  Could it be that the 'Reals' option in Solve[] is not being applied, or is Mathematica trying to be 'smart' in the way that it shows the solution?

Thanks,
dan

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