content_image/307655.jpg content_image/307654.jpg content_image/307653.jpg content_image/307652.jpg content_image/307651.jpg content_image/307650.jpg
It is clear that inequality (16) contradicts (10). On the other hand, integrating inequality (14) from n to n + 1, we get 

<img src='content_image/307655.jpg'>

Since z ( t ) is nonincreasing for t > T, from the above inequality, we obtain that 

and so, we have 

<img src='content_image/307654.jpg'>

<img src='content_image/307653.jpg'>

In view of (15), (8), and (9), we obtain from the above inequality that 

and 

Since n ≤ s < n + 1 , (17) contradicts (11). 

<img src='content_image/307652.jpg'>

<img src='content_image/307651.jpg'>

Case 2 . τ ≤ 1 . Then z ( t − τ ) ≤ z ([ t − 1]) for n + 1 > t ≥ n > T, and from (13), we obtain that 

<img src='content_image/307650.jpg'>

9 

