x-y+z=0,2x+y-2z=6,3x-y-z=3求解,

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x-y+z=0,2x+y-2z=6,3x-y-z=3求解,
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x-y+z=0,2x+y-2z=6,3x-y-z=3求解,
x-y+z=0,2x+y-2z=6,3x-y-z=3求解,

x-y+z=0,2x+y-2z=6,3x-y-z=3求解,
{x-y+z=0,①
2x+y-2z=6,②
3x-y-z=3 ③
①+②,得3x-z=6 ④
③-①,得2x-2z=3,
即x-z=1.5 ⑤
④-⑤,得2x=4.5
∴x=2.25
把x=2.25代入⑤,得
2.25-z=1.5
z=0.75
把x=2.25,z=0.75代入①,得
2.25-y+0.75=0
y=3
∴原方程组的解是：{x=2.25
y=3
z=0.75

(1)+(2)得
3x-z=6 (4)
(2)+(3)得
5x-3z=9 (5)
(4)×3-(5)得
4x=9
x=9/4
把x=9/4代入(4)得
z=3/4
把x=9/4,z=3/4代入(1)得
9/4-y+3/4=0
y=3
∴方程组的解为
x=9/4
y=3
z=3/4

x-y+z=0,
2x+y-2z=6, （2）
3x-y-z=3 （3）
（1）+（2）, (2)+(3)
3x-z=6
5x-3z=9
4x=9
x=9/4
z=6-3x=-3/4
y=3/2

x-y+z=0 (1)
2x+y-2z=6 (2)
3x-y-z=3 (3)
(1)+(2)式得：3x-z=6
(2)+(3)式得：5x-3z=9
移项：z=3x-6
带入(2)+（3）式得：5x-9x+18=9
解得：x=9/4
将x=9/4带回（2）+（3）式得：y=3
将x=9/4 y=3/2带回（1）式得z=3/4

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