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一、选择题(只有一个选项是正确的)l、设等差数列1“,}的前n项和为、,二nZ+bn+c,al等于( (D)4anz一‘ .撒一 贝(A)l/2 二3,(B)2(C)1/4 2、函数少=ASin(、+,)(。o、八井0)的图象与函数y二Acos(~十沪)(。0、A并0)的图象在区间(.T。,二。十二)上(). 田 (A)至少有两个交点 (B)至
First, the multiple-choice questions (only one option is correct) l, set the first n and equal, and two nZ+bn+c, al equal ((D) 4anz a. (A)l/2 2 3, (B) 2 (C) 1/4 2, less function = ASin (, +,) (. O, 8 wells 0) image and function Y two Acos (~ ten Shanghai The image of () 0, A, and 0) is in the interval (.T., 2. Twelve) (). Field (A) has at least two intersections (B) to