2016-1等差数列复习VIP免费

._________:),274(:)172.._____,38,203._______,30,240,18S2._______,,21}1.{a1111324911110nbannnSSSnaSaSSdnSnnnnnn则（项和之比为若两个等差数列的前则）若则）若则首项）若公差项和，为前为等差数列，一、自我小测二、自主整理等差数列的概念1.等差数列的通项公式2.公式等差数列的求和3.4.性质：(1)m+n=p+qam+an=ap+aq(2)等差数列中,依次每k项之和仍为等差数列.nnnnnnnaaaaaaaa求为等差数列求证；满足若数列例)2(;11)1(0232,1:}{:111132)2(::1nnnaaa易得证1113211111nnnnnaaaaa32111nnnaaa21342nannnnnnnnnanaaaaaaaaa求满足若数列),2(,1,2:}{:111121练习nnnaaa21111APan为}1{nan2nnnaSSSSSnaS求的等差中项为与，的等比中项为与项和的前是等差数列例,143543,}{:243543dnanSdan21,,:则公差为设首项为解2)23()()2()23)((2dadadadada512401dada或nnnnnnTnnSTSSnaSa求项和的前为数列项和前为为等差数列设,,75,7,}{,}{:157练习1,21da解：252211ndnanSnnnTn49412d求公差：比为偶数项和与奇数项和之项中在前项和为等差数列的前例,273212,35412:32732225662256621112123541121dadada：解法5d27323542奇偶偶奇：解法SSSS162192奇偶SSdSS6奇偶1n2Sa,n1nSSaSS1n2)2(aaSS,ndSSn2)1(}a{1n21n1n1nnn偶奇偶奇偶奇奇偶时，则项数为时，则项数为中点评：在等差数列?,,053}{)3(.,,,25,}{)2(0S,0,0,0,}{)1(41138917176761中最大的是多少则项和为其前且中在等差数列并求此最大值问数列前多少项和最大中在等差数列？立的最大自然数是多少成项和则使其前是等差数列设例ｎnnnnnSnSaaaaSSaanaaaaaa