排序原理:设a_1≥a_2≥…≥a_n,b_1≥b_2≥…≥b_n,则a_1b_1+a_2b_2+…+a_nb_n≥a_1b_1+a_2b_t_2+…+a_nb_t_n≥a_1b_n+a_2b_(n-1)+…+a_nb_1.(Ⅰ)并且(Ⅰ)式中等号成立的充要条件是a_1=a_2=…=a_n或b_1=b_2=…=b_n(其中b_t_1,b_t_2,…,b_t_n是b_1,b_2,…,b_n的一个排列). 限于篇幅,上述原理的证明留给读者完 Sorting principle: Let a_1≥a_2≥...≥a_n, b_1≥b_2≥...≥b_n, then a_1b_1+a_2b_2+...+a_nb_n≥a_1b_1+a_2b_t_2+...+a_nb_t_n≥a_1b_n+a_2b_(n-1)+...+a_nb_1.(I (1) The necessary and sufficient condition for the equality of (I) is that a_1=a_2=...=a_n or b_1=b_2=...=b_n (where b_t_1, b_t_2,..., b_t_n is an arrangement of b_1, b_2,..., b_n). Due to space limitations, the proof of the above principle is left to the reader