设{an}为等差数列,{bn}为等比数列又a1=b1,a3=b3,a7=b5.比较的a15和b7大小关系,给出证明
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人气：240 ℃ 时间：2019-11-12 08:50:44
解答
{an}为等差数列,公差为da3=a1+2da7=a1+6da15=a1+14d{bn}为等比数列,公比为qb3=b1q^2b5=b1q^4b7=b1q^6∵a1=b1a3=b3∴a1+2d=b1q^2b1+2d=b1q^22d=b1(q^2-1)——(1)而a7=b5则a1+6d=b1q^4b1+6d=b1q^46d=b1(q^4-...
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