(1) Thanks--- I didn't know about gcd == 'algebraic.
(2) gcd == subres with algebraic == false is a trouble maker:
(C1) p : x^3+x+1$
(C2) sol : first(solve(p,x))$
(C3) gcd : subres$
(C4) algebraic : true$
These are all okay:
(C5) ratsimp(subst(sol,p));
(D5) 0
(C6) gcd : spmod$
(C7) ratsimp(subst(sol,p));
(D7) 0
(C8) algebraic : false$
(C9) ratsimp(subst(sol,p));
(D9) 0
But gcd == subres and algebraic == false causes trouble
(C10) gcd : subres$
(C11) ratsimp(subst(sol,p));
QUOTIENT by ZERO
-- an error. Quitting. To debug this try DEBUGMODE(TRUE);)
(C12) gcd : spmod$
(C13) ratsimp(subst(sol,p));
(D13) 0
Does algebraic default to false just for speed? Or is there a _good_
reason to
default it to false?
Barton