仔细观察各个方程,利用消元法就好
(1)y=z-x①
2x-3y+2z=5②
x+2y+z=13③
(3)*2-(2)得:y=3
代入(1)和(3)
得:z-x=3,z+x=3
相加:z=5,x=2
(2)x-y=6①
x+z=4②
2x-y+2z=12③
(2)*2-3得:y=-4代入(1),得:x=2.代入(2)得z=2
3.a+b+c=-6①
a-b+c=-8②
4a+2b+c=-11③
(1)+(2)得:a+c=-7-----(4)
(1)-(2)得:b=1
代入(3)4a+c=-13-----(5)
(4)-(5)得 a=-2, c=-5