1.在等差数列{an}中,a1+a5=8,a4=7,则a5= ( )
A.11 B.10 C.7 D.3
2.已知{an}是公差为1的等差数列,Sn为{an}的前n项和,若S8=4S4,则a10=
( )
A. B. C.10 D.12
3.(2020·沈阳模拟)在等差数列{an}中,若Sn为前n项和,2a7=a8+5,则S11的值是
( )
A.55 B.11 C.50 D.60
4.(2019·全国卷Ⅰ)记Sn为等差数列{an}的前n项和.已知S4=0,a5=5,则
( )
A.an=2n-5 B.an=3n-10
