Let $(C, A) \in \mathbb{C}^{p \times n} \times \mathbb{C}^{n \times n}$ be an observable pair and let $\mathbf{u}(\lambda)=\mathbf{u}_0+\lambda \mathbf{u}_1+\cdots+\lambda^k \mathbf{u}_k$ be a vector polynomial with coefficients in $\mathbb{C}^n$. Show that $C\left(\lambda I_n-A\right)^{-1} \mathbf{u}(\lambda)$ has a pole at $\alpha$ if and only if $\left(\lambda I_n-A\right)^{-1} \mathbf{u}(\lambda)$ has a pole at $\alpha$. [HINT: Try Exercise 19.16 first to warm up.]