for simple case 2*2,  A = matrix([[0,-1],[1,0]]);

using A, i understand f(x,y) = f(-y,x)

where do other case f(-x,-y) and f(y,-x) come from?

any command to list all cases with input a matrix A?

if A has more dimensions, what will the cases be ?

how to x1, x2 ... with xi in procedure?

b := 1;

for i = 1 to 3 do

     b := b*1/(1-xi);

od;

but xi can not represent x1, x2, x3, which commands can present x1 x2 x3 ?

which package containing command to find prime ideal and quotient of ideal?

How to assign value to matrix in procedure?

with(ArrayTools):
kontraHom := proc(M, s)
dim := Size(M);
n := dim[1];
m := dim[2];
R := [][];
for i from 1 to m do
    for j from 1 to s do
        for k from 1 to n do
            R[(j-1)*n+k,(j-1)*m+i] = M[i,k];
        od;
    od;    
od;

c := y^2+2*y*x+x^2-y^2*x-y*x^2

solve(c);

{x = -y, y = y}, {x = y/(-1+y), y = y}

above polynomial find roots using solve

if do reverse to find back its polynomial c from {x = -y, y = y}, {x = y/(-1+y), y = y}

any command to do this? is it possible to do this? which book teach this?