x+6y=5√xy
(√x-2√y)(√x-3√y)=0
√x=2√y
√x=3√y
所以x=4y或x=9y
√x=2√y
原式=(8y+2y-y)/(4y+2y+2y)=9/8
√x=3√y
原式=(18y+3y-y)/(9y+3y+2y)=10/7