數(shù)列基礎(chǔ)練習(xí)題及答案

1、數(shù)列專題1.數(shù)列1,3,7,15,的通項(xiàng)公式an等于()A. 2nB.2n1C.2n1D.2n122. 各項(xiàng)不為苓的等差數(shù)列 an中,2a3 a7 + 2an= 0,數(shù)列bn是等比數(shù)列,且 b7=a7,那么 b6b8=().A. 2B. 4C. 8D. 163. 等差數(shù)列an, a6 2,貝u此數(shù)列的前11項(xiàng)的和S11A. 44B. 33C. 22D. 114.等差數(shù)列an的公差d0 , a1 20,且a7, a9成等比數(shù)列.Sn為a的前n項(xiàng)和,那么Sw的值為(A.110C. 905.等比數(shù)列an滿足a1)B.90D. 110a2 3, a2 a3 6 ,貝U a7( )A. 646.anB.

2、 81C.是等比數(shù)列,a128D. 243,14, a4,那么公比q =(2)1A、一27.數(shù)列B、2an是公差不為C、20的等差數(shù)列,a2,且a2,1D、一2a3, a4 1成等比數(shù)列.(1)求數(shù)列 an的通項(xiàng)公式;(2)設(shè)bn ,求數(shù)列 a的前n項(xiàng)和Sn .n an 28.設(shè)數(shù)列an是首項(xiàng)為1 ,公差為d的等差數(shù)列,且a,a2 1,83 1是等比數(shù)列bn的前三項(xiàng).(1)求an的通項(xiàng)公式；(2)求數(shù)列bn的前n項(xiàng)和Tn.9.等差數(shù)列an滿足a3=5, as- 2a2=3,又等比數(shù)列bn中,b=3且公比q=3.(1) 求數(shù)列an, bn的通項(xiàng)公式；(2) 假設(shè)Ch=an + bn,求數(shù)列cn的

3、前n項(xiàng)和Si.10. 設(shè)等比數(shù)列 an的前n項(xiàng)和為Sn,a2 6, 6a1 a3 30 ,求an和Sn.11. an是公差不為零的等差數(shù)列,a = 1,且a1, a3, a9成等比數(shù)列.(I)求數(shù)列an的通項(xiàng)；(n )求數(shù)列2an的前n項(xiàng)和Sn.12 .等差數(shù)列 an (n N )的前n項(xiàng)和為Sn,且a3 5,S3 9.求數(shù)列an的通項(xiàng)公式；(II)設(shè)等比數(shù)列 bn (n N),假設(shè)b2 a2,b3 a5,求數(shù)列bn的前n項(xiàng)和Tn.13 .an是首項(xiàng)為19,公差為-2的等差數(shù)列,Sn為(an的前n項(xiàng)和.(I)求通項(xiàng)an及Sn ；(n)設(shè)bn an是首項(xiàng)為1,公比為3的等比數(shù)列,求數(shù)列bn的通項(xiàng)公式及其前 n項(xiàng)和Tn參考答案1 . C2.D3.C4.D5.A7.(1)an2n；(2)&n .n 18.(1)an2n1； (2)Tn2n 1.9.(1)an2n1,bn3n?2 2 3n1 33 , 2) n210.an32口 1或an2 3n1 , Sn3(2n 1)或 Sn3n 111 .(1)ann(2)Sn2n 1 2.12.(I)an2nn .314/ II T1,("