已知数列{a n }的前n项和S n =n 2 +(a-1)n;数列{b n }满足2b n =(n+1)a n 。 (1)若a 1 ,a 3 ,a 4 成等比数列,求数列{a n }的通项公式; (2)若对任意的n∈N*都有b n ≥b 5 成立,求实数a的取值范围; (3)数列{c n }满足c n -c n-2 =3·(- ) n-1 (n∈N*且n≥3,其中c 1 =1,c 2 =- ; f(n)=b n -|c n |,当-16≤a≤-14时,求f(n)的最小值(n∈N*)。
【简答题】CSC Co is a health food company producing and selling three types of high-energy products: cakes, shakes and cookies, to gyms and health food shops. Shakes are the newest of the three products and wer...