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2x4y3z 9 3x2y5z 11

(1)+(2)×2得 8x+13z=31 (4) (2)×3-(3)得 4x+8z=20 (5) (5)×2-(4)得 3z=9 ∴z=3 把z=3代入(4)得 8x+39=31 ∴x=-1 把x=-1,z=3代入(1)得 -2+4y+9=9 ∴y=1/2

解: 2x+4y+3z=9.................(1) 3x-2y+5z=11 ..............(2) 5x-6y+7z=13...............(3) (1)+(2)*2: 8x+13z=31...................(4) (2)*3-(1): 4x+8z=20,x+2z=5....(5) (5)代入(4): 8(5-2z)+13z=31 -3z=-9 z=3 x=5-2z=-1 y=0.5 ...

先化简①2x+4y+3z=9②3x-2y+5z=11 6x-4y+10z=22 9x-6y+15z=33③5x-6y+7z=13①+2×②可化简为8x+13z=313×②-③=4x+8z=20然后可以求出z=3 x=-1 在求出y=1/2

题目有点小问题

2x+4y+3z=9 ① 3x-2y+5z=11 ② 5x-6y+7z=13 ③ ①+②得:5x+2y+8z=20 ④ ④-③得:8y+z=7 ⑤ ⑤+4×②得:12x+21z=51,整理得:4x+7z=17 ⑥ ③-⑥得:x-6y=-4 ⑦ ④-⑥得:x+2y+z=3 ⑧ 4×⑧-⑥得:2x-3z=-5 ⑨ ⑥-2×⑨得:13z=27,z=13/27,所以x=-16/9,y=10/27

2x+4y+3z=9,① 3x-2y+5z=11,② 5x-6y+7z=13 ③ ①+②×2,得8x+13z=31 ④ ②×3-③,得4x+8z=20 ⑤ ④-⑤×2,得-3z=-9,解得z=3 代入⑤,解得x=-1 代入①,解得y=0.5

解:由题意 2x+4y+3z=9 (1式) 3x-2y+5z=11 (2式) 5x-6y+7z=13 (3式) (2式)*3: 9x-6y+15z=33(4式) (4式)-(3式): 4x+8z=20 (5式) (2式)*2: 6x-4y+10z=22 (6式) (1式)+(6式): 8x+13z=31 (7式) (5式)*2: 8x+16z=40 (8式) (8式)-(7式): 3z=9,...

2x+4y+3z=9① 3x-2y+5z=11② 5x-6y+7z=13 ③ ①+②×2得8x+13z=31 ④ ②×3-③得4x+8z=20 ⑤ ④-⑤×2得-3z=-9解得z=3 代入⑤解得x=-1 代入①解得y=0.5

2x+4y+3z=9 ① 3x-3y+5z=11 ② 5x-6y+z=13 ③ 7y+7z=7 ①+②-③ y+z=1 16y+6.5z=9.5 ①x2.5-③ 9.5y=3 y=3/9.5=6/19 z=6.5/9.5=13/19 x=54/19 x=54/19 y=6/19 z=13/19还有什么疑问请追问

解: 2x+4y+3z=9.................(1) 3x-2y+5z=11 ..............(2) 5x-6y+7z=13...............(3) (1)+(2)*2: 8x+13z=31...................(4) (2)*3-(1): 4x+8z=20,x+2z=5....(5) (5)代入(4): 8(5-2z)+13z=31 -3z=-9 z=3 x=5-2z=-1 y=0.5

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