\hsize 0pt\vsize 0pt\nopagenumbers\overfullrule 0pt\noindent$$\eqalign{v(n) &= x(n) - \beta(1 + \alpha)v(n - 1) - \alpha v(n - 2)\cry(n) &= \alpha v(n) + \beta(1 + \alpha) v(n - 1) + v(n - 2)}$$\bye