Thus the Routh tabulation is continued as

As there is one sign change in the first column, one of the roots is on the right hand side of the w -plane. This implies that one root in z -plane lies outside the unit circle.

To verify our conclusion, the roots of the polynomial , are found out to be z = 0.5, z = -0.8 and z = 2. Thus one can see that z = 2 lies outside the unit circle and it is inverse of z = 0.5 which caused the all zero row in w -plane.