K766 :a*b^2*x^2*y - a^2*c*x^2*y - a^2*b*x*y^2 + b^2*c*x*y^2 + a^2*b*x^2*z - a*c^2*x^2*z - a*b^2*y^2*z + b*c^2*y^2*z + a^2*c*x*z^2 - b*c^2*x*z^2 - b^2*c*y*z^2 +  a*c^2*y*z^2 = 0