[必做题] 已知整数n≥4,集合M={1,2,3,…n}的所有3个元素的子集记为A 1 ,A 2 ,…,A C . (1)当n=5时,求集合A 1 ,A 2 ,…,A C 中所有元素之和; (2)设m i 为A i 中的最小元素,设p n =m 1 +m 2 +…+m c ,试求p n (用n表示).
【简答题】A.Castles' structure and the eating habit in them. B.Castles' structure and people who lived in them. C.Castles' structure and the lives in them. D.Why people built castles and castles' structure.
【简答题】A.Castles' structure and the eating habit in them. B.Castles' structure and the people who lived in them. C.Castles' structure and the life in them. D.Why people built castles and their structure.