# Singular

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 Post subject: "Factor" questionPosted: Thu Aug 11, 2005 5:33 pm
Hi,

My question is certainly a simple one, however I did not guessed the point.

In the Help Manual "D.7.5.2 Factor" you give the following Example:

LIB "zeroset.lib";
ring R = (0,a), x, lp;
minpoly = a2+1;
poly f = x4 - 1;
list fl = Factor(f);
fl;
==> [1]:
==> _[1]=1
==> _[2]=(40a+60)*x+(40a+60)
==> _[3]=(1/65a-29/130)*x+(-1/65a+29/130)
==> _[4]=(4a)*x+4
==> _[5]=(7/520a+1/130)*x+(1/130a-7/520)
....

- which is just (x-1)*(x+1)*(x-a)*(x+a) where the factors are modified by some invertible elements of Q(a)[x] having their product = 1. (some complex rationals actually)

My question is: what is the property that single out the Singular answer in the above example, out of the many others, which all just differ by invertible factors?

Horvath Sandor

email: shorvath@ms.sapientia.ro
Posted in old Singular Forum on: 2005-02-01 11:59:03+01

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 Post subject: Posted: Tue Sep 20, 2005 5:05 pm

Joined: Fri Apr 29, 2005 12:02 am
Posts: 24
Location: Germany, Kaiserslautern
Dear Sandor Horvath,

the command "Factor" from zeroset.lib is obsolete. Nowadays you should use the function "factorize":

Code:
> ring R = (0,a), x, lp;
> minpoly = a2+1;
> poly f = x4 - 1;
> factorize(f);
[1]:
_[1]=1
_[2]=x-1
_[3]=x+1
_[4]=x+(a)
_[5]=x+(-a)
[2]:
1,1,1,1,1

Sincerely,

The Singular Team

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