$\left\{\begin{matrix}F=\frac{x_{2}+7}{x}\text{, }&x\neq 0\\F\in \mathrm{C}\text{, }&x_{2}=-7\text{ and }x=0\end{matrix}\right.$

$\left\{\begin{matrix}x=\frac{x_{2}+7}{F}\text{, }&F\neq 0\\x\in \mathrm{C}\text{, }&x_{2}=-7\text{ and }F=0\end{matrix}\right.$

$\left\{\begin{matrix}F=\frac{x_{2}+7}{x}\text{, }&x\neq 0\\F\in \mathrm{R}\text{, }&x_{2}=-7\text{ and }x=0\end{matrix}\right.$

$\left\{\begin{matrix}x=\frac{x_{2}+7}{F}\text{, }&F\neq 0\\x\in \mathrm{R}\text{, }&x_{2}=-7\text{ and }F=0\end{matrix}\right.$