2023-2024学年天一大联考·安徽卓越县中联盟高三(上)期中考试数学.考卷答案

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2023-2024学年天一大联考·安徽卓越县中联盟高三(上)期中考试数学.考卷答案试卷答案

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分析(1)由Sn=an-1(a>0,且a≠1),可得当n=1时,a1=a-1,a2=S2-S1.可得等比数列{an}的公比q=$\frac{{a}_{2}}{{a}_{1}}$.由于6a1,a3,a2成等差数列,可得6a1+a2=2a3,代入即可得出.
(2)bn=$\frac{{2}^{n}}{({2}^{n-1}+1)({2}^{n}+1)}$=$2(\frac{1}{{2}^{n-1}+1}-\frac{1}{{2}^{n}+1})$.利用“裂项求和”即可得出.

解答解:(1)∵Sn=an-1(a>0,且a≠1),∴当n=1时,a1=a-1,a2=S2-S1=(a2-1)-(a-1)=a(a-1).
∴等比数列{an}的公比q=$\frac{{a}_{2}}{{a}_{1}}$=a.∵6a1,a3,a2成等差数列,∴6a1+a2=2a3,6a1+a1a=$2{a}_{1}{a}^{2}$,化为2a2-a-6=0,a>0,解得a=2.∴an=2n-1
(2)bn=$\frac{{a}_{n+1}}{({a}_{n}+1)({a}_{n+1}+1)}$=$\frac{{2}^{n}}{({2}^{n-1}+1)({2}^{n}+1)}$=$2(\frac{1}{{2}^{n-1}+1}-\frac{1}{{2}^{n}+1})$.
∴Tn=$2[(\frac{1}{2}-\frac{1}{3})+(\frac{1}{3}-\frac{1}{5})$+…+$(\frac{1}{{2}^{n-1}+1}-\frac{1}{{2}^{n}+1})]$=2$(\frac{1}{2}-\frac{1}{{2}^{n}+1})$=$\frac{{2}^{n}-1}{{2}^{n}+1}$.

点评本题考查了等差数列与等比数列的通项公式、“裂项求和”、递推关系的应用,考查了推理能力与计算能力,属于中档题.