lim an＝lim [(2n+1)an]/(2n+1)＝lim [(2n+1)an] × lim 1/(2n+1)＝3×0＝0
所以,3＝lim [(2n+1)an]＝2×lim nan ＋ lim an＝2×lim nan
所以,lim nan ＝ 3/2