\documentclass{article}
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\begin{document}\begin{center}
 E(R_{i,t})=E(\alpha_i)+E(\beta_{i,F_1 } F_{1,t})+E(\beta_{i,F_2 } F_{2,t})+\ldots+E(\beta_{i,F_m } F_{m,t})\linebreak
\bar{R}_{i,t}=a+\hat{\beta}_{i,F_1 } E(F_{1,t})+\hat{\beta}_{i,F_2 } E(F_{2,t})+\ldots+\hat{\beta}_{i,F_m } E(F_{m,t})\linebreak
\bar{R}_{i,t}=a+\gamma_1\hat{\beta}_{i,F_1 } +\gamma_2\hat{\beta}_{i,F_2 } F_{2,t}+\ldots+\gamma_m\hat{\beta}_{i,F_m }
\end{center}\end{document}