A linear time-invariant discrete-time system is described by the vector matrix difference equation $$ x(k+1)=F \underline{X}(k)+G \underline{u}(k) $$
Where $\underline{X}(k)$ is the state vector, $F$ is an $n \times n$ constant matrix, $G$ is a $(n \times r)$ constant matrix and $\underline{u}(k)$ is the control vector. The state transition matrix of the system is given by inverse $Z$-transform of
- $ZI - F$
- $(Z I-F) Z$
- $(Z I-F)^{-1} G$
- $(Z I-F)^{-1} Z$