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\begin{document}
\begin{align*} 
{\bar F}(t)&={\bar F}_1(t){\bar F}_2(t)+{\bar F}_3(t){\bar F}_4(t){\bar F}_5(t)-{\bar F}_6(t){\bar F}_7(t){\bar F}_8(t){\bar F}_9(t){\bar F}_{10}(t){\bar F}_{11}(t){\bar F}_{12}(t){\bar F}_{13}(t){\bar F}_{14}(t){\bar F}_1(t)\\
&={\bar G}_1(t){\bar G}_2(t)+{\bar G}_3(t){\bar G}_4(t){\bar G}_5(t)-{\bar G}_6(t){\bar G}_7(t){\bar G}_8(t){\bar G}_9(t){\bar G}_{10}(t){\bar G}_{11}(t){\bar G}_{12}(t){\bar G}_{13}(t){\bar G}_{14}(t){\bar G}_1(t)
\end{align*}
\end{document}