数列an前n项和Sn,满足a1=tSn-(2t+1)S(n-1)=t,t>0,n>=21,证数列an是等比数列.
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数列an前n项和Sn,满足a1=tSn-(2t+1)S(n-1)=t,t>0,n>=21,证数列an是等比数列.
数列an前n项和Sn,满足a1=tSn-(2t+1)S(n-1)=t,t>0,n>=2
1,证数列an是等比数列.
数列an前n项和Sn,满足a1=tSn-(2t+1)S(n-1)=t,t>0,n>=21,证数列an是等比数列.
tSn-(2t+1)S(n-1)=t
当n为n+1时
tSn+1-(2t+1)Sn=t
两个式子相减就可以的到an+1和an的关系了,当然这时候是在n大于等于2可以说明他是等比数列
在利用已知计算处a2,说明他的等比和上式的公比相同就可以了
懂了吗
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