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94年全国高考“3+2”型数学试题(理)25题是: 设{a_n}是正数组成的数列,其前n项和为S_n并且对于所有的自然数n,a_n与2的等差中项等于S_n与2的等比中项。 (1)写出数列{a_n}的前3项; (1)求数列{a_n}的通项公式(写出推证
The 25 questions of the “3+2” mathematics test questions in the national college entrance examination in 1994 are: Let {a_n} be a series of positive numbers, and the first n terms are S_n and for all natural numbers n, the difference between a_n and 2 The term is equal to the equal term of S_n and 2. (1) Write the first three terms of the series {a_n}; (1) Find the general formula of the series {a_n}