资阳高三文科数学答案第 1 页(共 4 页)资阳市高中 2015 级第二次诊断性考试文科数学参考答案及评分意见一、选择题:本大题共12 小题,每小题5 分,共 60 分
C 二、填空题:本大题共5 小题,每小题4 分,共 20 分
2或3.三、解答题 :共70分
(一) 必考题 :共 60 分
17.(12 分)(1)当1n时,1122aa,解得12a,当2n时,22nnSa,1122nnSa
所以122nnnaaa,则12nnaa,所以 {}na是以 2 为首项, 2 为公比的等比数列
故112nnnaa q
···············································································4 分(2)22 log 22nnnnbn, 则231222322nnTn①23412122232(1)22nnnTnn②①- ②得:23122222nnnTn12(1 2 )212nnn11222nnn
所以1(1) 22nnTn. ······································································12 分18.(12 分)(1)由题,3
56t,76y,61()()iiittyy( 2
5) ( 0
8,621()iitt222222( 2
5b,又 aybt ,得70
44a,资阳高三文科数学答案第 2 页(共 4