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\left\{\begin{array}{l} S_{1}=\bar{S}+a_{1} F_{1}+a_{2} F_{1}^{2}+\cdots+a_{l-1} F_{1}^{l-1}+a_{l} F_{1}^{l} \\ S_{2}=\bar{S}+a_{1} F_{2}+a_{2} F_{2}^{2}+\cdots+a_{l-1} F_{2}^{l-1}+a_{l} F_{2}^{l} \\ \ldots \\ S_{l}=\bar{S}+a_{1} F_{l}+a_{2} F_{l}^{2}+\cdots+a_{l-1} F_{l}^{l-1}+a_{l} F_{l}^{l} \\ T=\bar{S}+a_{1} T+a_{2} T^{2}+\cdots+a_{l-1} T^{l-1}+a_{l} T^{l} \end{array}\right.