K655 :

a^2*c^2*x^2*y + c^4*x^2*y - b^2*c^2*x*y^2 - c^4*x*y^2 - a^2*b^2*x^2*z - b^4*x^2*z + a^4*y^2*z + a^2*b^2*y^2*z + b^4*x*z^2 + b^2*c^2*x*z^2 - a^4*y*z^2 - a^2*c^2*y*z^2 = 0