x+y+z=2,xy+yz+xz=1.求x^2y^2z^2
问题描述：
x+y+z=2,xy+yz+xz=1.求x^2y^2z^2
答
(x+y+z)^2=x^2+y^2+z^2+2xy+2xz+2yz=4
so x^2+y^2+z^2=4-2=2