Denote the nth, mth-order polynomial sets(n>m) with real coefficients as F={f(z)|f(z)=a_0z~n+a_1z~(n-1)+…+a_(n-1)z+a_n,a_0≠0}, G={g(z)|g(z)=b_0z~m+b_1z~(m-1)+…+b_(m-1)z+b_m, b_0≠0}.For any f(z), if all its roots lie within the unit circle, then f(z) is said to be astable polynomial in the discrete time sense, and denoted as f(z)∈S. For any g(z)∈G, f(z)∈F∩S, define Denote the nth, mth-order polynomial sets (n> m) with real coefficients as F = {f (z) | f (z) = a_0z ~ n + a_1z ~ (n-1) + ... + a_ (n-1 g + z - a + b - m + b - m - 1 z + b - m, b - 0 ≠ 0} For any f (z), if all its roots lie within the unit circle, then f (z) is said to be astable polynomial in the discrete time sense, and denoted as f (z) εS. For any g ( z) ∈G, f (z) ∈F∩S, define