4x-9z=17 3x+y+15z=18 x+2y+3z=2

问题描述:

4x-9z=17 3x+y+15z=18 x+2y+3z=2
x+y+z=26 x-y=1 2x+z-y=18

4x-9z=17(1)
3x+y+15z=18(2)
x+2y+3z=2(3)
(2)*2得:6x+2y+30z=36(4)
(4)-(3)得:5x+27z=34(5)
(1)*3得:12x-27z=51(6)
(5)+(6)得:.17x=85,x=5
将x=5带入(1)得z=1/3
将x=5.z=1/3带入(2)得:y=-2
所以x=5.y=-2.z=1/3
2)x+y+z=26(1)
x-y=1(2)
2x+z-y=18(3)
(3)-(1)得:x-2y=-8(4)
(2)-(4)得:y=9
将y=9带入(2)得:x=10
将x=10,y=9带入(1)得z=7
所以x=10,y=9,z=7