1.已知a,b,c满足a+2b-5c=0①,a-2b+c=0②,求a:b:c2.解三元一次方程组:3x+2y+z=6①2x+y+3z=1②x+3y+2z=5③

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1.已知a,b,c满足a+2b-5c=0①,a-2b+c=0②,求a:b:c2.解三元一次方程组:3x+2y+z=6①2x+y+3z=1②x+3y+2z=5③1.已知a,b,c满足a+2b-5c=0①

1.已知a,b,c满足a+2b-5c=0①,a-2b+c=0②,求a:b:c2.解三元一次方程组:3x+2y+z=6①2x+y+3z=1②x+3y+2z=5③
1.已知a,b,c满足a+2b-5c=0①,a-2b+c=0②,求a:b:c
2.解三元一次方程组:
3x+2y+z=6①
2x+y+3z=1②
x+3y+2z=5③

1.已知a,b,c满足a+2b-5c=0①,a-2b+c=0②,求a:b:c2.解三元一次方程组:3x+2y+z=6①2x+y+3z=1②x+3y+2z=5③
1.1+5*2式:
6a-8b=0
a:b=4:3
c=2b-a
c:b=2-a/b=2:3
a:b:c=4:3:2.
2.3*1-2式:
7x+5y=17
2*1-3式:
5x+y=7
18x=18
x=1
y=2
z=-1.

1.由1和2相加,得a=2c;
1和2相减,得b=3/2c;
刚可知a:b:c=2c:3/2c:c=4:3:2
2.由(1)-(2)*2得
x=4+5z (4)
(2)-(3)*2得
y=(9-z)/2 (5)
把(4)(5)代入(1)可求得z,再把z值代入(4)(5)可求得结果

1、①-②得 b=3/2c;
代入①得a=2c;
所以设c=2t;则a=4t,b=3t;
所以a:b:c=4t:3t:2t=4:3:2
2、2×②-①得x+5z=-4 ④
3×②-①得5x+7z=-2 ⑤
由④⑤解得x=1,z=-1
把x,z代入②得 y=2.