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\begin{equation*}
    0 = \frac{v_1 - v_2}{R_1} - C_1 \frac{dv_2}{dt},\qquad
    0 = C_1 \frac{dv_2}{dt} + \frac{v_3}{R_2} + C_2 \frac{dv_3}{dt}.
\end{equation*}
\end{document}