等比数列{an}中前n项和Sn=3^n+r,则r等于( )A.-1 B.0 C.1 D.3
问题描述:
等比数列{an}中前n项和Sn=3^n+r,则r等于( )
A.-1 B.0 C.1 D.3
答
等比数列{an}中前n项和Sn=3^n+r,则r等于( )
A.-1 B.0 C.1 D.3