Giải PT sau bằng LG :$$\left\{\begin{matrix} & (1+x^2+x^2y+y)^2=8(x^2+x^2y) & \\ & (1+y^2+y^2z+z)^2=8(y^2+y^2z) & \\ & (1+z^2+z^2x+x)^2=8(z^2+z^2x) \end{matrix}\right.$$