首先等比數(shù)列an中 有命題：m+n=k+h 則 aman=akah
于是 a1*a10=a2*a9=a3*a8=.=a5*a6=25
對(duì)數(shù)運(yùn)算法則：log(ab)=log(a)+log(b)
log(a)表示以m為底,a的對(duì)數(shù),
所以
log以5為底a1的對(duì)數(shù)+log以5為底a2的對(duì)數(shù)……+log以5為底a10
=log[a1a2a3.*a10]
=log[(a1a10)(a2a9)(a3a8)(a4a7)(a5a6)]
=log[25^5]
=log[5^10]
=10