(1) A+B =(-xy+yz+xz)+(-2xy+yz-xz)=-xy+yz+xz-2xy+yz-xz=-3xy+2yz(2) 3A-2B =3(-xy+yz+xz)-2(-2xy+yz-xz)=-3xy+3yz+3xz+4xy-2yz+2xz=xy+yz+5xz