当4x-3y-6z=0,x=2y-7z=0时,求（x方+2y方+5z方）/(x方+3y方+z方）快

当4x-3y-6z=0,x=2y-7z=0时,求（x方+2y方+5z方）/(x方+3y方+z方）快
当4x-3y-6z=0,x=2y-7z=0时,求（x方+2y方+5z方）/(x方+3y方+z方）
快

当4x-3y-6z=0,x=2y-7z=0时,求（x方+2y方+5z方）/(x方+3y方+z方）快
4x-3y-6z=0 (1)
x+2y-7z=0 (2)
(1)*2+(2)*3
8x+3x-12z-21z=0
z=x/3
(1)*7-(2)*6
28x-6x-21y-12y=0
y=2x/3
所以y²=(4/9)x²,z²=(1/9)x²
所以原式=[x²+(8/9)x²+(5/9)x²]/[x²+(12/9)x²+(1/9)x²]
=(22/9)x²/(22/9)x²
=1