吉林省延吉市金牌教育中心高中数学第二章数列基础训练A组新人教A版必修51.在数列55,34,21,,8,5,3,2,1,1x中,x等于()A.11B.12C.13D.142.等差数列9}{,27,39,}{963741前则数列中nnaaaaaaaa项的和9S等于()A.66B.99C.144D.2973.等比数列na中,,243,952aa则na的前4项和为()A.81B.120C.168D.1924.12与12,两数的等比中项是()A.1B.1C.1D.215.已知一等比数列的前三项依次为33,22,xxx,1那么2113是此数列的第()项A.2B.4C.6D.86.在公比为整数的等比数列na中,如果,12,183241aaaa那么该数列的前8项之和为()A.513B.512C.510D.8225二、填空题1.等差数列na中,,33,952aa则na的公差为______________。2.数列{na}是等差数列,47a,则7s_________在等差数列na中,,1.3,3.0125aa求2221201918aaaaa的值。2求和:)0(),(...)2()1(2anaaan设等比数列na前n项和为nS,若9632SSS,求数列的公比q金牌教研中心高中数学训练题()参考答案(数学5必修)第二章[基础训练A组]一、选择题4.C2(21)(21)1,1xx5.B2(33)(22),14,14xxxxxxx或而133313,134(),422222nxqnx6.C332112131(1)18,()12,,2,22qaqaqqqqqq或而89182(12),2,2,2251012qZqaS二、填空题1.85233985252aad2.4971747()7492Saaa3.12651955199"55199199()2792652929312()2aaaaaaSbbbbSbb34.337563310925,5,755qqaaq5.2471102aaaa6.112n111111...242422333log33...3log(333)log(3)nnn211[1()]111122...11222212nnn三、解答题解:设四数为3,,,3adadadad,则22426,40aad即1333,222ad或,当32d时,四数为2,5,8,11当32d时,四数为11,8,5,2解:1819202122201255,72.8,0.4aaaaaaaadd201283.13.26.3aad∴18192021222056.3531.5aaaaaa解:原式=2(...)(12...)naaan2(1)(...)2nnnaaa2(1)(1)(1)12(1)22naannaanna解:显然1q,若1q则3619,SSa而91218,Sa与9632SSS矛盾由369111369(1)(1)2(1)2111aqaqaqSSSqqq496332333120,2()10,,1,2qqqqqqq得或而1q,∴243q5