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等比数列若= ( )
A.7 B.8 C.15 D.16
等比数列的前项和为,, 若成等差数列,则 ( )
A.7 B. 8 C.16 D.15
等比数列的前项和为,且成等差数列.若,则=( )
等比数列的前项和为,, 若成等差数列,则( )
A. 7 B. 8 C. 16 D.15
等比数列的前n项和为,且4,2,成等差数列。若=1,则=( )
A.16 B.15 C.8 D.7