解方程组
2x-3y-z=0
x+3y-14z=0
得：
x=5z
y=3z
( 4x²-5xy+z²)/(xy+yz+xz)
=(4*25z^2-5*5z*3z+z^2)/(15z^2+3z^2+5z^2)
=26z^2/23z^2
=26/23