x/3=y/2=z/5,(xy+yz+zx)/(x²+y²+z²)=
问题描述:
x/3=y/2=z/5,(xy+yz+zx)/(x²+y²+z²)=
答
设x/3=y/2=z/5=k
则x=3k,y=2k,z=5k
∴,(xy+yz+zx)/(x²+y²+z²)=(6k²+10k²+15k²)/(9k²+4k²+25k²)=31/38