a13a1a3a521的精选

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已知等比数列{an}满足a1=3,a1+a3+a5=21,则a3+a5+a7=           （  ） ...

已知等比数列{an}满足a1=3,a1+a3+a5=21,则a3+a5+a7=           （  ） ...

2022-08-12
问题详情：已知等比数列{an}满足a1=3,a1+a3+a5=21,则a3+a5+a7=           （  ）                                    A.21          B.42         ...