已知4x-3y-6z=0,x+2y-7z=0.求2x²+3y²+6z²/x²+5y²+7z²的值.已知4x-3y-6z=0,x+2y-7z=0,求2x²+3y²+6z²/x²+5y²+7z²的值.

已知4x-3y-6z=0,x+2y-7z=0.求2x²+3y²+6z²/x²+5y²+7z²的值.已知4x-3y-6z=0,x+2y-7z=0,求2x²+3y²+6z²/x²+5y²+7z²的值.
已知4x-3y-6z=0,x+2y-7z=0.求2x²+3y²+6z²/x²+5y²+7z²的值.
已知4x-3y-6z=0,x+2y-7z=0,
求2x²+3y²+6z²/x²+5y²+7z²的值.

已知4x-3y-6z=0,x+2y-7z=0.求2x²+3y²+6z²/x²+5y²+7z²的值.已知4x-3y-6z=0,x+2y-7z=0,求2x²+3y²+6z²/x²+5y²+7z²的值.
4x-3y-6z=0.(1)
x+2y-7z=0.(2)
(2)*4-(1),得
11y-22z=0
y=2z
(1)*2+(2)*3,得
11x-33z=0
x=3z
把X=3Z,y=2z代入
2x^2+3y^2+6z^2/x^2+5y^2+7z^2
=[2*(3z)^2+3*(2z)^2+6z^2]/[(3z)^2+5*(2z)^2+7z^2]
=36z^2/(36z^2)
=1

由原方程组解得x=3z,y=2z
代人得1

有已知两式求解，x=7z-2y,带入前式得y=2z,再带入得x=3z,然后带入下面的式子，化简得18x²+12x²+6x²/9x²+20x²+7x²=36/36=1

先解方程组：4x-3y-6z=0，x+2y-7z=0;目的是用z表示x,y;结果得y=2z,x=3z;代入2x²+3y²+6z²/x²+5y²+7z²后得答案等于1.