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

4x-3y-6z=0 (1)x+2y-7z=0 (2)(1)*2+(2)*38x+3x-12z-21z=0z=x/3(1)*7-(2)*628x-6x-21y-12y=0y=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)x&su...