Andreas Enge on Thu, 20 Sep 2012 15:27:05 +0200 |
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Re: polresultant disagrees with sage, maxima and magma |
On Thu, Sep 20, 2012 at 04:09:07PM +0300, Georgi Guninski wrote: > I don't claim this is a bug in pari, more like a bug in the > mentioned CAS. > > ? p1=x2*(x3-x4);p2=x2*(x3-2*x4);polresultant(p1,p2,x1) > %1 = 0 > > Since p1 and p2 certainly have common roots I expect the resultant > w.r.t. x1 (not present in p1 or p2) to be able to vanish. As a polynomial in x1, both polynomials are constant and non-zero and so do not have roots. The correct result should be 1. Also interesting: ? polresultant(x,y,z) %1 = x ? polresultant(y,x,z) %2 = x And: ? polresultant(x,y,x) %7 = y All of these should be 1, if I understand resultants correctly. Andreas