N:=15; X:=y^2 + (x^2 + x + 1)*y + x^2; r:=1+(x*y+y^2) / (x^2*(x+y+1)); s:=1+y/(x*(x+1)); E:=[s-r*s+1,r*s-r^2*s,r*s-r^2*s,0,0]; P:=[0,0];