已知数列{An}的前n项和为Sn,且满足A1=2,AnAn+1=4Sn对任意n属于正整数都成立..求A2,A3,A4.
问题描述:
已知数列{An}的前n项和为Sn,且满足A1=2,AnAn+1=4Sn对任意n属于正整数都成立..求A2,A3,A4.
答
A1A2 = 4S1
2A2 = 8=> A2 = 4S2 = 6
A2A3 = 4S2 = 24 => A3 = 6S3 = 12
A3A4 = 4S3 = 48 => A4 = 8