[sage-support] Re: solve() not finding all roots

2009-07-16 Thread Marshall Hampton
If phcpack does not report any 'failure' solutions in classified_solution_dicts(), then it should have found all the roots. But the groebner methods are preferable if you are interested in exact solutions. -Marshall On Jul 16, 11:29 am, Doug wrote: > > The last element of that Groebner basis is

[sage-support] Re: solve() not finding all roots

2009-07-16 Thread Doug
> The last element of that Groebner basis is a univariate polynomial in > x2, so it is relatively easy to analyze its solutions.  There is one > triple root at x2=0, and then four others which are presumably the > four you are thinking of.  Once you have a value for x2, you can > substitute it int

[sage-support] Re: solve() not finding all roots

2009-07-16 Thread Marshall Hampton
The last element of that Groebner basis is a univariate polynomial in x2, so it is relatively easy to analyze its solutions. There is one triple root at x2=0, and then four others which are presumably the four you are thinking of. Once you have a value for x2, you can substitute it into the othe

[sage-support] Re: solve() not finding all roots

2009-07-16 Thread Doug
I confess I'm not a mathematician (I'm an economist) and it's been almost 25 years since I took a basic course in abstract algebra. But this is interesting. From the wikipedia page on Grobner bases, it seems I should be able to compute solutions to the system based on the Grobner basis, but I ca

[sage-support] Re: solve() not finding all roots

2009-07-16 Thread David Joyner
Does this help any? sage: R = PolynomialRing(QQ, 2, 'x1,x2', order='lp') sage: x1,x2 = R.gens() sage: f1 = 1/2*((x1^2 + 2*x1 - 4)*x2^2 + 2*(x1^2 + x1)*x2 + x1^2) sage: f2 = 1/2*((x1^2 + 2*x1 + 1)*x2^2 + 2*(x1^2 + x1)*x2 - 4*x1^2) sage: I = (f1,f2)*R; I Ideal (1/2*x1^2*x2^2 + x1^2*x2 + 1/2*x1^2 +