25^x=2000
则
25^(xy)=2000^y=25^y*80^y
80^y=2000
则
80^(xy)=2000^x=25^x*80^x
*
(25*80)^xy=25^(x+y)*80^(x+y)
则
xy=x+y
1/X+1/Y
=(x+y)/xy
=1
祝你学习天天向上,加油!