65 A determinant formula for realization by SISO

Let $T(s)$ be a proper rational function. Then $T(s)$ can be realised as the transfer function of a SISO $(A,B,C,D)$, so $T(s)=D+C{(sI-A)}^{-1}B$. In particular, with $A,B,C$ as in frame 57 and $D\in 𝐂$,

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