[질문] x+y+z=1, xy+yz+zx=2, xyz=3 일때 (x+y)(y+z)(z+x)의 값을 알려주세요

(x+y)(y+z)(z+x) = (1-z)(1-x)(1-y) = <--- x+y+z=1이므로(1-x-z+xz)(1-y) =1-x-z+xz-y+xy+yz-xyz =1-(x+y+z)+(xy+yz+xz)-xyz =1-1+2-3 = -1