x, y, z, l, a, b, c, 
(c^2-l^2)*y^2+(b^2-l^2)*z^2+(-a^2+b^2+c^2-2*l^2)*y*z
(a^2-l^2)*z^2+(c^2-l^2)*x^2+(a^2-b^2+c^2-2*l^2)*z*x
(b^2-l^2)*x^2+(a^2-l^2)*y^2+(a^2+b^2-c^2-2*l^2)*x*y
