已知数列 an 的前n项和为sn,满足an+Sn=3-8/2的n次方设bn=2的n次方乘an
已知数列 an 的前n项和为sn,满足an+Sn=3-8/2的n次方设bn=2的n次方乘an
求证;数列bn是等差数列
求证;数列bn是等差数列
其他人气:271 ℃时间:2019-10-08 06:08:52
优质解答
由题:Sn = 3 - 8/2^n - anSn-1 = 3 - 8/2^(n-1) - an-1an = Sn - Sn-1 = [3 - 8/2^n - an] - [3 - 8/2^(n-1) - an-1]= 8/2^(n-1) - 8/2^n - an + an-1两边同时 +an:2an = 8/2^(n-1) - 8/2^n + an-1两边同乘以2^(n-...
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