若x:y:z=2:7:5,且x-2y+3z=6

问题描述:

若x:y:z=2:7:5,且x-2y+3z=6
若x:y:z=2:7:5,且x-2y+3z=6,求(x+y)除以z² 注.“:”是比的意思

设x=2k,y=7k,z=5k
x-2y+3z=6
2k-14k+15k=6
k=2
(x+y)/z^2=(2k+7k)/(5k)^2=9k/25k^2=9/(25k)=9/(25*2)=9/50