设等比数列{an}的前n项和为Sn,若Sm=93,am=48,q=2.则m

设等比数列{an}的前n项和为Sn,若Sm=93,am=48,q=2.则m
设等比数列{an}的前n项和为Sn,若Sm=93,am=48,q=2.则m

设等比数列{an}的前n项和为Sn,若Sm=93,am=48,q=2.则m
am = a1 * q^(m-1) = a1 * 2^(m-1) = 48 （2^(m-1)是2的 m-1 次方） ①式
Sm = a1 * ( 1 - q^m ) / ( 1 - q ) = a1 * ( 2^m - 1 ) = 93 ②式
①式除以②式得
2^(m-1) / ( 2^m - 1 ) = 48 / 93
-> 2^m / ( 2^m - 1 ) = 96 / 93 = 32 / 31
-> 2^m = 32
-> m = 5

m=5
楼上的解题就对了