三元一次方程x+y+z=0,2x-y+z=-15,x+2y-z=40.x+y+z=02x-y+z=-15x+2y-z=40

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三元一次方程x+y+z=0,2x-y+z=-15,x+2y-z=40.x+y+z=02x-y+z=-15x+2y-z=40
三元一次方程x+y+z=0,2x-y+z=-15,x+2y-z=40.
x+y+z=0
2x-y+z=-15
x+2y-z=40

三元一次方程x+y+z=0,2x-y+z=-15,x+2y-z=40.x+y+z=02x-y+z=-15x+2y-z=40
x+y+z=0 (1)
2x-y+z=-15 (2)
x+2y-z=40 (3)
(1)+(3) 2x+3y=40 (4)
(2)+(3) 3x+y=25 (5)
(5)*3-(4) 7x=35 得x=5
再将x=5代入(5)得y=10
然后将x=5,y=10代入(1)得z=-15

x=5 y=10 z=-15

5;10;-15

x=5;y=10;z=-15