1:7x+2y-z=7 2:6x-y+z=7 3:4x+3y+z=9 1:9x+4y+z+10 2:-9X+2y+3z=-6 3:3x-4y+2z=5 1:3x-5y+2z=1 2:4X+5y-z=5 3:x-5y+3z=-2 1:5x-3y+6z=-3 2:2X-y+3z=0 3:y+3z=6
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1:7x+2y-z=7 2:6x-y+z=7 3:4x+3y+z=9 1:9x+4y+z+10 2:-9X+2y+3z=-6 3:3x-4y+2z=5 1:3x-5y+2z=1 2:4X+5y-z=5 3:x-5y+3z=-2 1:5x-3y+6z=-3 2:2X-y+3z=0 3:y+3z=6
1:7x+2y-z=7
2:6x-y+z=7
3:4x+3y+z=9
1:9x+4y+z+10
2:-9X+2y+3z=-6
3:3x-4y+2z=5
1:3x-5y+2z=1
2:4X+5y-z=5
3:x-5y+3z=-2
1:5x-3y+6z=-3
2:2X-y+3z=0
3:y+3z=6
1:7x+2y-z=7 2:6x-y+z=7 3:4x+3y+z=9 1:9x+4y+z+10 2:-9X+2y+3z=-6 3:3x-4y+2z=5 1:3x-5y+2z=1 2:4X+5y-z=5 3:x-5y+3z=-2 1:5x-3y+6z=-3 2:2X-y+3z=0 3:y+3z=6
(一)
①+②,得13x+y=14④
①+③,得11x+5y=16⑤
④*5,得65x+5y=70⑥
⑥-⑤,得x=1
把x=1代入④,得y=1
把x=1,y=1代入②,得z=2
(二)
①+③,得12x+3z=15④
②*2,得-18x+4y+6z=-12⑤
⑤-③,得-15x+8z=-7⑥
④*8,得96x+24z=120⑦
⑥*3,得-45x+24z=-21⑧
⑦-⑧,得x=1
把x=1代入④,得z=1
把x=1,z=1代入①,得y=0
(三)
①+②,得7x+z=6④
②+③,得5x+2z=3⑤
④*2,得14x+2z=12⑥
⑥-⑤,得x=1
把x=1代入①,得z=-1
把x=1,z=-1代入①,得y=0
(四)
①*2,得10x-6y+12z=-6④
②*5,得10x-5y+15z=0⑤
⑤-④,得y+3z=6⑥
⑥-③,得0=0
(所以,无解/恒解)