等比数列{an}是递减数列,其前n项的积为Tn,若T13＝4T9,则a8·a15等于( )A.±2 ... 问题详情：等比数列{an}是递减数列,其前n项的积为Tn,若T13＝4T9,则a8·a15等于( )A.±2 B.±4 C.2 ...
