√x(√x+√y)=3√y(√x+5√y)
x-2√xy-15y=0
(√x-5√y)(√x+3√y)=0
因为x>0,y>0
所以√x=5√y
x=25y
代入后式得到：
[2x+(√xy)+3y]/[x+(√xy)-y]
=(50y+5y+3y)/[25y+5y-y]
=2