已知二分之x=三分之y=四分之z,求xy+yz+zx分之x²+y²+z²

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已知二分之x=三分之y=四分之z,求xy+yz+zx分之x²+y²+z²已知二分之x=三分之y=四分之z,求xy+yz+zx分之x²+y²+z

已知二分之x=三分之y=四分之z,求xy+yz+zx分之x²+y²+z²
已知二分之x=三分之y=四分之z,求xy+yz+zx分之x²+y²+z²

已知二分之x=三分之y=四分之z,求xy+yz+zx分之x²+y²+z²
设x/2=y/3=z/4=k
则x=2k,y=3k,z=4k
(x²+y²+z²)/(xy+yz+zx)
=(4k²+9k²+16k²)/(6k²+12k²+8k²)
=29k²/26k²
=29/26

令x/2=y/3=z/4=m,则x=2m,y=3m,z=4m
xy+yz+zx分之x²+y²+z²
=(4m^2+9m^2+16m^2)/(6m^2+12m^2+8m^2)
=29/26

设a=x/2=y/3=z/4
那x=2a,y=3a,z=4a
(x²+y²+z²)/(xy+yz+zx)=(4a²+9a²+16a²)/(6a²+12a²+8a²)=29a²/26a²=29/26

答案如图:

x/2=y/3=z/4
得 x=2/3y z=4/3y
原式=(2/3y*y+y*4/3y+4/3y*2/3y)/(4/9y^2+y^2+16/9y^2)
=26/29