已知x/2=y/3=z/-1≠0,求分式2x+6y-3z/x+y+2z的值
问题描述：
已知x/2=y/3=z/-1≠0,求分式2x+6y-3z/x+y+2z的值
答
设 x/2=y/3=z/-1=a
x=2a y=3a z=-a
(2x+6y-3z)/(x+y+2z)
=(4a+18a+3a)/(3a)
=25a/3a
=25/3