4000-5-10-15-∠∠∠∠∠∠-95-100=???

2025-02-25 16:11:54
推荐回答(1个)
回答1:

an =5n

4000-5-10-15-...-95-100
=4000-(a1+a2+...+a20)
=4000-10(5+100)
=4000-1050
=2950