极限思想是一种基本而又重要的数学思想 ,灵活地借助极限思想解题 ,可以避开抽象且复杂的运算 ,优化解题过程 ,降低解题难度 .例 1　已知数列 an 中 ,a1=1且对于任意自然数n ,总有an+1=anan- 2 ,是否存在实数a ,b ,使得an =a -b(- 23) n 对于任意自然数n恒成立 ?若存在 ,给出证 Limit idea is a basic and important mathematical thought, flexible limit solution by means of the limit, you can avoid abstract and complex operations, optimize the problem-solving process and reduce the difficulty of solving problems.Example 1 known sequence an, a1 = 1 and for any natural number n there is always an + 1 = anan- 2, is there a real number a, b such that an = a -b (- 23) n holds for any natural number n?