Niu Ke practice 16 B beautiful tree [hash/thinking]

\begin{align}\notag \dot{x}&=\mathbf{A}x+\mathbf{B}u\\y&=\begin{bmatrix}1&0\\0&1\end{bmatrix}x+\begin{bmatrix}1&0\\0&1\end{bmatrix}u\end{align}