3x+2y-z=1 x-2y+2z=5 5x-2y+5z=11 3x+2y-z=1 ①x-2y+2z=5 ②5x-2y+5z=11 ③①-3*②得 8y-7z=-14 ④5*①-3*③得 16y-20z=-28 ⑤2*④-⑤得 6z=0 z=0代入z到④,得y=-7/4代入y和z到①,得x=3/2因此 x=3/2 y=-7/4 z=0o(∩_...