(10分)已知数列{an}满足a1=3,an+1= an +2n, (1)求{ an }的通项公式an; (2)若bn= (10分)已知数列{an}满足a1=3,an+1= an +2n, (1)求{ an }的通项公式an; (2)若bn=n an,求数列{bn}的前n项和s 分类:证券交易(旧版) 题型:判断题 查看答案