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\usepackage{amsmath}
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\usepackage{bm}
\begin{align}
\label{eq:l}
\dot{\lambda_t} = &\dfrac{(\alpha+(1-\alpha)(1-e^{\eta_t}))((1-\chi)e^{\eta_t}+\chi)-\alpha(1-e^{\eta_t})}{(1-\chi)e^{\eta_t}+\chi-\alpha} \ e^{(\alpha-1)\lambda_t} \\
\nonumber
&-\dfrac{e^{\frac{\chi-1}{\chi} \delta_t}(1-e^{\eta_t})^{\frac{1}{\chi}}(1-\alpha)^{\frac{1}{\chi}}((1-\chi)e^{\eta_t}+\chi)}{(1-\chi)e^{\eta_t}+\chi-\alpha} e^{(\frac{\alpha}{\chi}-1)\lambda_t} \\
&+\dfrac{\rho(1-e^{\eta_t})}{(1-\chi)e^{\eta_t} +\chi-\alpha},
\end{align}
ちなみに、TeXShop 4.57, macOS 11.1 です。