已知x+y+z=1,x²+y²+z²=2求xy+yz+xz的值

问题描述:

已知x+y+z=1,x²+y²+z²=2求xy+yz+xz的值

(x+y+z)²=1 ,x²+2xy+y²+2(x+y)z+z²=1,x²+y²+z²+2(x+y)z+2xy=1
xy+yz+xz=-1/2