Prove that the condition that the plane ux+vy+wz=0 may cuts rhe cone ax^2+by^2+cz^2=0 in perpendicu

Prove that the condition that the plane ux+vy+wz=0 may cuts rhe cone ax^2+by^2+cz^2=0 in perpendicular generators if (b+c)u^2+(c+a)v^2+(a+b)w^2=0