问题 填空题 正项等比数列中1a2a4+2a42+1a4a6=81,则1a3+1a5=______. 答案 由题意,∵1a2a4+2a42+1a4a6=81∴(1a3+1a5)2=81∵正项等比数列∴1a3+1a5=9故答案为9