\hsize 0pt\vsize 0pt\nopagenumbers\overfullrule 0pt\noindent$$\eqalign{v(n) &= x(n) - a_1 v(n - 1) - a_2 v(n - 2) \cry(n) &= b_0 v(n) + b_1 v(n - 1) + b_2 v(n - 2)}$$\bye