Study of the asymptotic behavior of the solutions of three systems of difference equations of exponential form

In this paper we study the boundedness, the persistence and the asymptotic behavior of the positive solutions of the following systems of two difference equations of exponential form:xn+1=α+βe-ynγ+yn-1,yn+1=δ+ϵe-xnζ+xn-1,xn+1=α+βe-ynγ+xn-1,yn+1=δ+ϵe-xnζ+yn-1,xn+1=α+βe-xnγ+yn-1,yn+1=δ+ϵe-ynζ+xn-1,where α, β, γ, δ, ϵ, ζ are positive constants and the initial values x−1, x0, y−1, y0 are positive constants.