4x-3y-6z=0,x+2y-7z=0,xyz的积不等于0,求(x+y-z)/(x-y+2z)的值
问题描述:
4x-3y-6z=0,x+2y-7z=0,xyz的积不等于0,求(x+y-z)/(x-y+2z)的值
答
4X-3Y-6Z=0
4X-3Y=6Z①
X+2Y-7Z=0
X+2Y=7Z②
①-②×4:-11Y=-22Z
Y=2Z
将Y=2Z代入②
X=3Z
(X+Y-Z)/(X-Y+2Z)=(3Z+2Z-Z)/(3Z-2Z+2Z)=4Z/(3Z)=4/3