1/7专题数列一、单选题1.(2025·全国二卷·高考真题)记nS为等差数列na的前n项和,若356,5,SS则6S()A.20B.15C.10...
1/34专题数列一、单选题1.(2025·全国二卷·高考真题)记nS为等差数列na的前n项和,若356,5,SS则6S()A.20B.15C.10...