2019年高考数学(文科)二轮专题突破训练：专题四 数列 专题能力训练11 含答案.pdfVIP

专题能力训练11 等差数列与等比数列 一、能力突破训练 1.已知等比数列{a }满足a =,aa =4(a -1),则a = ( ) n 1 3 5 4 2 A.2 B.1 C. D. 2.在等差数列{a }中,a +a+a=3,a +a +a =87,则此数列前20项的和等于( ) n 1 2 3 18 19 20 A.290 B.300 C.580 D.600 3.设{a }是等比数列,S {a }的前n项和.对任意正整数n,有a +2a +a =0,又a =2,则S 的值为 n n n n n+1 n+2 1 101 ( ) A.2 B.200 C.-2 D.0 4.已知{a }是等差数列,公差d不为零,前n项和 S ,若a ,a ,a 成等比数列,则( ) n n 3 4 8 A.ad0,dS 0 B.ad0,dS 0 1 4 1 4 C.ad0,dS 0 D.ad0,dS 0 1 4 1 4 5.在等比数列{a }中,满足a +a+a+a+a=3, =15,则a -a +a-a +a 的值 n 1 2 3 4 5 1 2 3 4 5 ( ) A.3 B. C.- D.5 6.在数列{a }中,a =2,a =2a ,S 为{a }的前n项和.若S =126,则n= . n 1 n+1 n n n n 7.已知等比数列{a }为递增数列,且 =a ,2(a +a )=5a ,则数列的通项公式a = . n 10 n n+2 n+1 n 8.设x,y,z是实数,若9x,12y,15z成等比数列,且 成等差数列,则 = . Ⅲ 9.(2018全国 ,文17)在等比数列{a }中,a =1,a =4a . n 1 5 3 (1)求{a }的通项公式; n (2)记S 为{a }的前n项和,若S =63,求m. n n m 10.已知等差数列{a }和等比数列{b }满足a =b=1,a +a=10,bb =a. n n 1 1 2 4 2 4 5 (1)求{a }的通项公式; n (2)求和:b +b+b+…+b . 1 3 5 2n-1 11.设数列{a }满足a +3a +…+(2n-1)a =2n. n 1 2 n (1)