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\begin{equation*}
  \frac{d^ny}{dt^n}+a_1\frac{d^{n-1}y}{dt^{n-1}}+\cdots+
  a_ny=b_0\frac{d^{m}u}{dt^{m}}+b_1\frac{d^{m-1}u}{dt^{m-1}}+\cdots+ b_mu, 
\end{equation*}
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