已知数列{an}是等差数列,且bn=2的an次方,求证数列{bn}是等比数列
高二等比数列
人气:288 ℃ 时间:2019-08-19 15:22:27
解答
∵数列{an}是等差数列,
∴an-a(n-1)=d
∵bn/b(n-1)
=2^an/[2^a(n-1)]
=2^[an-a(n-1)]
=2^d
∴ {bn}是等比数列,公比为2^d
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