由log3an＋1＝log3an＋1(n∈N*)得,an＋1＝3an,∵an>0,∴数列{an}是公比等于3的等比数列,∴a5＋a7＋a9＝(a2＋a4＋a6)×33＝35,∴log1
3 (a5＋a7＋a9)＝－log3（3^5）＝－5