已知x+2y-4z=0,3x-y-z=0,则3x+2y+z/x+2y+z=
问题描述：
已知x+2y-4z=0,3x-y-z=0,则3x+2y+z/x+2y+z=
答
x+2y-4z=0 (1)
3x-y-z=0,(2)
(2)*2+(1)得
6x-2y-2z+x+2y-4z=0
7x=6z
x=6z/7
y=11z/7
则3x+2y+z/x+2y+z
=(3*6z/7+2*11z/7+z)/(6z/7+2*11z/7+z)
=(47z/7)/(35z/7)
=47/35