2x-y-z=0 ①
3x+2y-12z=0 ②
①×2+②得7x-14z=0
x=2z
把x=2z代入①得y=3z
(2z²+3xy+y²)/(y²+z²)
=(2z²+18z²+9z²)/(9z²+z²)
=29z²/(10z²)
=29/10
如果2x=y+z 3x+2y-12z=0且z≠0,求（2z²+3xy+y²）/（y²+z&
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