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D.2.4.19 discrim

Procedure from library grobcov.lib (see grobcov_lib).

Usage:
discrim(f,x);
poly f: the polynomial in Q[a][x] or Q[x] of degree 2 in x poly x: can be a variable or a parameter of the ring.

Return:
the factorized discriminant of f wrt x for discussing its sign

Example:
 
LIB "grobcov.lib";
if(defined(R)){kill R;}
ring R=(0,a,b,c),(x,y),dp;
short=0;
poly f=a*x^2*y+b*x*y+c*y;
discrim(f,x);
==> [1]:
==>    _[1]=-1
==>    _[2]=y
==>    _[3]=(4*a*c-b^2)
==> [2]:
==>    1,2,1