الفهرس 
Summary
The basic definitions and theoremsOnly 14 pages are availabe for public view
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Abstract
In this thesis we study the qualitative behavior of solutions of certain difference equations. Recently, difference Equations have started to receive much attention from scientists and from various disciplines. Perhaps this is largely due to the advent of computers where differential equations are solved by using their approximate difference equations formulations. With the use of a computer one can easily experiment with difference equations and one can easily discover that such equations possess fascinating properties with a great deal of structure and regularity. Of course all computer observations and predictions must also be proven analytically. Therefore this is a fertile area of research, still in its infancy, with deep and important results. Difference equations play a very important role in many applications such as the natural model of a discrete process, ecology, mathematical models of various biological system etc. So, the main objective of this thesis is to shed light on nonlinear difference equations of different orders, through studying the qualitative behavior of solutions of those equations by different methods. More specifically, we study the following : - Equilibrium points for difference equations. - Local stability and global asymptotic stability of the solutions of difference equations. - Boundedness of solutions of difference equations. -The periodicity and oscillation of solutions of difference equations ; This thesis consists of five chapter, and a list of references. Chapter (1) it is an introduction and presented the overview and the entrance to the thesis and the last part is the thesis outline. In Chapter (2), we study a more general nonlinear rational difference equations with positive coefficients and positive initial conditions. In Chapter (3), we study the local stability, periodic character, global stability, boundedness of the positive solutions of class of nonlinear difference equations with positive real coefficients. In Chapter (4), we study the qualitative behavior of solutions of class of nonlinear higher order difference equations. In Chapter (5), we investigate the boundedness character, the periodicity character, the oscillatory, locally stable and the global stability of the positive solutions of nonlinear rational difference equation. Our results generalize and complement some of the previous results in the literature. Moreover, Some examples (with figures and tables) are considered to illustrate the main results.