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[Q] how to solve and evalutate a polynomial?
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Author:  youngsu [ Thu Aug 11, 2005 5:32 pm ]
Post subject:  [Q] how to solve and evalutate a polynomial?
if i have a polynomial f (ex : poly f = x2 - 1 )

i want to have f(1) ( f(1) = (1)^2-1 = 0 )
and want to solve f(x) = 0

How can i do this?

email: [email protected]
Posted in old Singular Forum on: 2004-10-11 19:23:40+02
Author:  levandov [ Thu Aug 11, 2005 8:29 pm ]
Post subject:  Re: [Q] how to solve and evalutate a polynomial?
Hi,
Quote:
> if i have a polynomial f (ex : poly f = x2 - 1 )
>
> i want to have f(1) ( f(1) = (1)^2-1 = 0 )
> and want to solve f(x) = 0
>
> How can i do this?

First of all you have define a ring (which includes a definition of a ground field and an ordering on monomials).
In your case let the ground field be Q, then your ring definition will be
Code:
ring r = 0,(x),dp;

Then you define your polynomial.
Code:
poly f = x^2 -1;

For evaluation there is a command "subst"
Code:
poly f1 = subst(f,x,1);

For "solving" you can use either factorization (for one polynomial)
Code:
factorize(f);

or, for systems of equations, see the library "solve.lib".

In any case, you find the detailed information in the documentation, available both on-line (for instance, at http://www.singular.uni-kl.de/Manual/2-0-5/index.htm) and in every distribution you dowload.

Best regards,
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