(a+b+c+d)^3=3a³+b³+c³+d³+3a²b+3ab²+3c²d+3cd²+3a²c+6abc+3ac²+6acd+3a²d+6abd+6bd²+6b²c+3bc²+6bcd+3b²d+3bd²
(a+b+c+d)^4=(a^4+b^4+c^4+d^4)+4(a^3b+a^3c+a^3d+ab^3+ac^3+ad^3+b^3c+b^3d+bc^3+bd^3+c^3d+cd^3)+6(a^2b^2+a^2c^2+a^2d^2+b^2c^2+b^2d^2+c^2d^2)+12(a^2bc+a^2bd+a^2cd+ab^2c+ab^2d+ac^2d+acd^2+b^2cd+bc^2d+bcd^2)+24(abcd).
