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Re: [Axiom-math] Pointer update please.


From: Ralf Hemmecke
Subject: Re: [Axiom-math] Pointer update please.
Date: Tue, 02 Dec 2014 09:08:14 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.2.0

> Since you are maintaining Groebner information,

Oh, do I? I'm just maintaining the translation of the ++ documentation
(available in the .spad files) to a web representation.

> I wanted to convert quadratics p(x)->Q(x') by finding n,m: x'=m*x+n; so
> I put.
> p(x)-q(x')=0
> x'-m*x-n=0
> and got an answer in terms f(n,m)x^2+g(n,m)*x+h(n,m)=0
> so then I had to set
> f(n,m)=0
> g(n,m)=0
> h(n,m)=0
> as a separate step.  Which worked fine to give me triangular output.
> I am questioning the second step; not that it's wrong, but IMO it
> shouldn't be necessary.
> Is there a technique to avoid that?

Hmmm... in the first step you get a condition for m and n that still
involves x. You get rid of the x by requiring that each coefficient is
zero. Then you get 3 equations for m and n in the coefficients of the
original quadratic polynomials that must simultaneously equate to zero.

No you solve these equations in whatever way and express m and n in
terms of the original coefficients. If you don't do the trick with
removing the x and getting 3 equations, it would still be there. So why
do you think there is another method for solving that problem?

Ralf





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