Tính (x^4+y^4+z^4) - (x^2+y^2+z^2)^2 - 2(x^2+y^2+z^2)(x+y+z)^2 + (x+y+z)^4

(x^4+y^4+z^4) - (x^2+y^2+z^2)^2 - 2(x^2+y^2+z^2)(x+y+z)^2 + (x+y+z)^4