fifference equation plotting

Hi mates! I want to plot k=1.5 Xk = (Xk-1/2)+((25*Xk-1)/(1+Xk-1^2))+(8*cos(1.2*k)); and zk = xk^2/20

please let me know how to plot them. they are difference equations.

Please

Thanks a lot P

[Walter Roberson]

Please rewrite this in MATLAB notation.