1、x-y-z=1 (1)
2x+y-3z=4(2)
3x-2y-z=-1 (3)
(1)*3
3x-3y-3z=3(4)
(4)-(2)
x-4y=-1(5)
(3)-(1)
2x-y=-2(6)
(5)*2
2x-8y=-2(7)
(6)-(7)
7y=0
y=0
代入(6)x=-1
代入(1)z=-2
2、a+b/2=c (1)
a/2-b-c=1 (2)
3a+b=-2 (3)
(1)代入(2)
a/2-b-(a+b/2)=1
-a/2-3b/2=1
a+3b=-2(4)
(3)*3
9a+3b=-6(5)
(5)-(4)
8a=-4
a=-1/2
代入(3)b=-1/2
代入(1)c=-3/4