一、填空題.
(1)數(shù)列圖像特征是_______________.
(2)數(shù)列{n-1/n+1}的前五項(xiàng)為_______________.
(3)等差數(shù)列{an}的通向公式為an=z-3(n-1),首項(xiàng)為________,公差_____.
(4)等差數(shù)列{an}中,a3=4,a49=36,則公差d等于_______________.
(5)等差數(shù)列{an}中a4+a10=15,則a3+a5+a8+a12=_______________.
(6)已知等差數(shù)列{an}中,a1=2,a4=8,則Sn_______________.
(7)數(shù)列{an}的通向公式為an=5,則Sn=_______________.
(8)等差數(shù)列{an}中,a3+a15=20,則Sn=_______________.