N N 1 1� �LIM 1 1 1    ��  ��

Câu 20. Ta có: 1.2 2.3 3.4¹  ¹  ¹  ^... n n



¹ 1



� �lim 1 1 1    ��  �� .�  �1nVậy ^lim 1.2 2.3 3.4^{1 1 1 ...} n n



¹ 1





¹



k k k    1 2 3 ...2