x-y-z=3.yz-xy-xz=3.则x²+y²+z²=?

问题描述:

x-y-z=3.yz-xy-xz=3.则x²+y²+z²=?

(x-y-z)^2-2(yz-xy-xz)=x^2+y^2+z^2=3