方法一
(log8 9/log2 3)
=(lg9/lg8)/(lg3/lg2)
=(2lg3/3lg2)/(lg3/lg2)
=(2/3)*(lg3/lg2)/(lg3/lg2)
=2/3
方法二
(log8 9/log2 3)
=log2^3 3^2/log2 3
=(2/3)log2 3/log 2 3
=2/3
logm^a n^b
=(b/a)logm n