x-y-z=-1 (1)
3x+5y+7z=11 (2)
4x-y+2z=-1 (3)
(1)×7+(2)
10x-2y=4
5x-y=2 (4)
(1)×2+(2)
6x-3y=-3
2x-y=-1 (5)
(4)-(5)
3x=3
x=1
代入(5)
2-y=-1
y=3
代入91)
z=x-y+1=-1
所以x=1,y=3,z=-1