根据恒等式:
x^4+y^4+z^4
=(x+y+z)(x^3+y^3+z^3)-(xy+yz+xz)(x^2+y^2+z^2)+xyz(x+y+z)
和x+y+z=1,x^2+y^2+z^2=3,x^3+y^3+z^3=5
可得:xy+yz+xz=[(x+y+z)^2-x^2+y^2+z^2]/2=-1
x^3+y^3+z^3
=(x+y+z)(x^2+y^2+z^2)-(xy+yz+xz)(x+y+z)+3xyz
3xyz=5-1*3+(-1)*1=1,则xyz=1/3
所以x^4+y^4+z^4=1*5-(-1)*3+(1/3)*1=25/3