| 2026年高考数学上海-9 |
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2026-10-10 17:45:14 |
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(5分)已知$\{a_{n}\}$为等差数列,$a_{1}=0$,$d$为公差,$S_{n}$为$\{a_{n}\}$的前$n$项和,若$S_{n}$中至少有两项位于$(0,1)$之间,则公差$d$的取值范围为____. 〖答案〗$(0,\dfrac{1}{3})$. 〖分析〗结合等差数列通项公式及求和公式即可求解. 〖解答〗解:若$d\leqslant 0$,显然$a_{n}\leqslant 0$,则$S_{n}\leqslant 0$不满足题意; 若$d > 0$,只需$\left\{\begin{array}{l}{S_{2}=0+d < 1}\\ {S_{3}=0+d+2d < 1}\end{array}\right.\Rightarrow d < \dfrac{1}{3}$, 故$d\in (0,\dfrac{1}{3})$. 故答案为:$(0,\dfrac{1}{3})$. 〖点评〗本题主要考查了等差数列通项公式及求和公式的应用,属于基础题.
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