x-y+2z=-1 (1)2x+y-z=-1 (2)3x-2y-2z=-9 (3)由(1)得y=x+2z+1,分别代入(2)、(3),得3x+z=-2 (4)x-6z=-7 (5)(4)×6+(5)19x=-19x=-1代入(4)z=-3x-2=-3(-1)-2=1y=x+2z+1=-1+2+1=2x=-1 y=2 z=1