设等比数列an的公比q =二分之一,前n项和为sn则a4分之s4=

设等比数列an的公比q =二分之一,前n项和为sn则a4分之s4=
设等比数列an的公比q =二分之一,前n项和为sn则a4分之s4=

设等比数列an的公比q =二分之一,前n项和为sn则a4分之s4=
S4/a4=[a1(1-q^4)/(1-q)]/(a1q^3)
=(1-q^4)/[(1-q)(q^3)]
=(1-1/16)/(1/16)
=15