Consider an AR(2) process with AR coe cients = ( 1 2).

(a) Show that the process is stationary for parameter values lying in the region 1 < 2 <1, 1 <1 2,and 1> 2 1.

(b) Showthatthepartial autocorrelation function of this process is 1 (1 2) for the rst lag, 2 for the second lag, and equal to zero for any lag h with h 3