log8(9)=A
log(2^3)(3^2)=A
(2/3)log2(3)=A
log2(3)=3A/2
lg3/lg2=3A/2 (换底公式）
log2(5)=B
lg5/lg2=B
(lg10-lg2)/lg2=B
(1-lg2)/lg2=B
解得lg2=1/(1+B)
所以lg3/lg2=3A/2为lg3/[1/(1+B)]=3A/2
解得lg3=3A/2(1+B)