Re: [Maxima-discuss] poly_discriminant

[Michel T. <ta...@lp...>]

Le 09/06/2021 à 16:09, Michel Talon a écrit :
>
> At what point has the polynomial been normalized i don't know.

In fact it is in  (rform (rform poly)).  It happens that rform invokes

ratf which gives the "rational" representation from the "general" 
representation and here:

(ratf poly) returns:

((MRAT SIMP ($X) (#:X763)) (#:X763 2 1 1 -2 0 6) . 2)

For rationals  fractions, P/Q are represented as dotted pair (P.Q)  
where polynomials P and Q are

as described previously.  It is clear that taking the rational 
representation has reduced  coefficients

to a common denominator. You can see this straightforwardly in the 
maxima command:

(%i7) rat(x^2/2-x+3);
                                   2
                                  x  - 2 x + 6
(%o7)/R/                         ------------
                                       2

This is the real origin of the discrepancy you have found in the 
computation of the discriminant to what you

expect.



-- 
Michel Talon