13x+11y+7z=709 11x+7y+13z=719 7x+13y+11z=711

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13x+11y+7z=709 11x+7y+13z=719 7x+13y+11z=711

13x+11y+7z=709 11x+7y+13z=719 7x+13y+11z=711
13x+11y+7z=709 11x+7y+13z=719 7x+13y+11z=711

13x+11y+7z=709 11x+7y+13z=719 7x+13y+11z=711
13x+11y+7z=709 1式
11x+7y+13z=719 2式
7x+13y+11z=711 3式
31X+31Y+31Z=709+719+711=2139
X+Y+Z=69 4式
X=69-Y-Z(代入2式和3式)
11*(69-Y-Z)+7y+13z=719
7* ( 69-Y-Z)+13y+11z=711
解得Y=22,Z=24 (代入4式)
解得X=23
答案是X=23,Y=22,Z=24
有点烦,但不难,耐心做,

解:
由方程组
13x+11y+7z=709 (1)
11x+7y+13z=719 (2)
7x+13y+11z=711 (3)
(2)*11-(1)*7,得
30x+94z=2946 (4)
(2)*13-(3)*7,得
94x+92z=4370 ...

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解:
由方程组
13x+11y+7z=709 (1)
11x+7y+13z=719 (2)
7x+13y+11z=711 (3)
(2)*11-(1)*7,得
30x+94z=2946 (4)
(2)*13-(3)*7,得
94x+92z=4370 (5)
(5)*47-(4)*46得
3038x=69874
得x=23
把x=23代入(4)得
30*23+94z=2946
94z=2256
得z=24
把x=23,z=24代入(1)得
13*23+11y+7*24=709
11y=242
得y=22.
∴方程组
13x+11y+7z=709 (1)
11x+7y+13z=719 (2)
7x+13y+11z=711 (3)
的解是:
x=23,
y=22,
z=24.

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