x-y-z=-1 3x+5y+7z=11 4x-y+2z=-1 分别求出x=?y=?z=?

x-y-z=-1 (1)
3x+5y+7z=11 (2)
4x-y+2z=-1 (3)
(1)*2+(3)得
6x-3y=-3
2x-y=-1(4)
所以2x-y=4x-y+2z=-1
x+z=0
代入（2）有5y+4z=5y-4x=11(5)
联立(4)(5)
x=1
y=3
所以
z=-1