K989 :

a^2 b^5 c^2 x^2 y-b^3 c^6 x^2 y-a^5 b^2 c^2 x y^2+a^3 c^6 x y^2+b^6 c^3 x^2 z-a^2 b^2 c^5 x^2 z-a^6 c^3 y^2 z+a^2 b^2 c^5 y^2 z-a^3 b^6 x z^2+a^5 b^2 c^2 x z^2+a^6 b^3 y z^2-a^2 b^5 c^2 y z^2=0