{x+4y-3z=0① 4x-5y+2z=0②
①×4-②:
(4x+16y-12z)-(4x-5y+2z)=0
∴21y-14z=0
∴y=2/3*z 代如入①
x+8/3z-3z=0
∴x=1/3*z
∴x:y:z=1:2:3
设x=t,y=2t,z=3t
则 (3x平方+2xy+z平方)除以(x平方+y平方)
=(3t²+4t²+9t²)/(t²+4t²)
=16t²/(5t²)
=16/5