数列的通项公式是解决数列问题的根基,梳理、优化出一套完整实用的公式,可为解决数列问题打下坚实的基础.一、优化公式Ⅰ——等差(比)数列的通项公式1.等差数列{a_n}:(1)a_n=a_1+(n-1)d=a_m+(n-m)d,其中n>m;(2)a_(n+1)-a_n=a_na_(n-1)=…=a_2-a_1=d;(3)若p+q=s+t,p,q, The general formula of series is to solve the problem of series, combing and optimizing a set of complete and practical formula, which can lay a solid foundation for solving the series of problems. 1. Equal-difference sequence {a_n} (1) a_n = a_1 + (n-1) d = a_m + (nm) d where n> m; a_n + 1 - a_n = a_na_n - 1 ) = ... = a_2-a_1 = d; (3) If p + q = s + t, p, q,