在等比数列中,怎么证明sn 与s2n-sn 和s3n-s2n成等比?
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人气：248 ℃ 时间：2020-06-29 03:53:11
解答
Sn = a1 * (q^n -1)/(q-1) S2n = a1 * (q^2n -1)/(q-1) S = a1 * [q^(k-1)n -1]/(q-1) Skn = a1 * [q^(kn) -1]/(q-1) S - S =[a1/(q-1)]*[q^(kn) - q^(k-1)n] = [a1/(q-1)] * q^[(k-1)n] * (q^n -1) = [a1 * (q^n -1...
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