数列的概念与表示.ppt

,单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,6.1 数列的概念与表示,1,2,3,4,5,6,题型,1,知数列前几项求通项公式,7,8,9,10,11,12,13,题型,2,由,a,n,与,S,n,的关系求通项公式,14,15,16,17,18,19,20,21,22,题型,3,由递推关系求通项公式,角度,1,形如,a,n,1,a,n,f,(,n,),，求,a,n,累加法,累乖法,23,24,25,26,待定系数法、转化法、构造法,角度,3,形如,a,n,1,pa,n,q,，求,a,n,角度,4,形如,a,n,1,pa,n,qb,n,，求,a,n,27,28,29,30,31,(2),已知在数列,a,n,中,a,1,=,1,a,n+,1,=,2,a,n,+,3,n,则数列的通项公式,a,n,=,.,32,(2),由,a,n+,1,=,2,a,n,+,3,n,得,a,n+,1,-,3,n+,1,=,2(,a,n,-,3,n,),.,所以数列,a,n,-,3,n,是首项为,a,1,-,3,1,=-,2,q=,2,的等比数列,所以,a,n,-,3,n,=-,2,2,n-,1,即,a,n,=,3,n,-,2,n,.,33,