课时标准练29等差数列及其前n项和

根底稳固组

1.(2025河南开封三模,文3)Sn为等差数列{an}的前n项和,假设S5=4a2,则a7=()

A.-2 B.0 C.2 D.10

2.(2025全国1,理9)记Sn为等差数列{an}的前n项和.S4=0,a5=5,则()

A.an=2n-5 B.an=3n-10

C.Sn=2n2-8n D.Sn=12n2-2

3.(2025河北沧州一模,理3)等差数列{an}的前n项和为Sn,a3=7,S3=9,则a10=()

A.25 B.32 C.35 D.40

4.等差数列{an}的首项a1=2,前n项和为Sn,假设S8=S10,则a1