can determine the poles of KG(s)H(s), since these poles arise from simple cascaded
first- or second-order subsystems. Further, variations in K do not affect the location
of any pole of this function. On the other hand, we cannot determine the poles of
TðsÞ ¼ KGðsÞ=½1 þ KGðsÞHðsÞ unless we factor the denominator. Also, the poles of
T(s) change with K.
Let us demonstrate. Letting