令a+b+c=x=0,ab+bc+ca=y,
则由4=a^2+b^2+c^2=x^2-2y知y=-2
a^4+b^4+c^4=(a^2+b^2+c^2)^2-2[(ab)^2+(bc)^2+(ac)^2]
=16-2(y^2-2x*abc)
=16-2y^2
=8
令a+b+c=x=0,ab+bc+ca=y,
则由4=a^2+b^2+c^2=x^2-2y知y=-2
a^4+b^4+c^4=(a^2+b^2+c^2)^2-2[(ab)^2+(bc)^2+(ac)^2]
=16-2(y^2-2x*abc)
=16-2y^2
=8