已知4x-3y-6z=0,x+2y-7z=0(x,y,z均不为0) ,求(2x+3y+6z)/(x+5y+5z)的值
来源:百度知道 编辑:UC知道 时间:2024/05/18 17:08:04
已知4x-3y-6z=0,x+2y-7z=0(x,y,z均不为0) ,求(2x+3y+6z)/(x+5y+5z)的值
4x-3y-6z=0...(1)
x+2y-7z=0...(2)
(2)*4-(1):
11y=22z
y=2z
代入(2):x+4z-7z=0
x=3z
将y=2z,x=3z代入(2x+3y+6z)/(x+5y+5z)
=(6z+6z+6z)/(3z+10z+5z)
=18z/18z
=1
由题可知:4x-3y=6z x+2y=7z
下式乘4减上式得出: (x+2y)*4-(4x-3y)=7z*4-6z
化简得:y=2z
将y=2z代入x+2y=7z ,得x+4z=7z,解得x=3z
将y=2z x=3z代入(2x+3y+6z)/(x+5y+7z),得
(6z+6z+6z)/(3z+10z+7z)=18z/20z=0.9
解方程组
4x-3y-6z=0
x+2y-7z=0
得:
x=3z,y=2z
(2x+3y+6z)/(x+5y+5z)
=(6z+6z+6z)/(3z+10z+5z)
=18z/18z
=1
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