x^4+4y^4=(x^2)^2+(2y^2)^2=(x^2)^2+(2y^2)^2+4x^2*y^2-4x^2*y^2=(x^2+2y^2)^2-4x^2*y^2=(x^2+2y^2-2xy)(x^2+2y^2+2xy)
貌似无解的样子
