the sum to infinity of a geometric sequence is 8/5 whereas t

the sum to infinity of a geometric sequence is 8/5 whereas the sum to infinity of the squares of the same geometric sequence is 64/15.Find the first term and the common ratio of the original geometric sequence.
lindaleeqqcool 1年前 已收到1个回答 举报
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psp2004 幼苗

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设等比级数的首项为a,公比为q,根据已知条件可知以下两个级数的和：
a+aq+aq^2+aq^3+...=8/5
a^2+(aq)^2+(aq^2)^2+(aq^3)^2+...=64/15
显然有|q|

1年前

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