$$x(1+\frac{R}{100})^{2}-x=\frac{x\times R\times4}{100}$$
$\left\{\begin{matrix}\\x=0\text{, }&\text{unconditionally}\\x\in \mathrm{C}\text{, }&R=200\text{ or }R=0\end{matrix}\right.$
$\left\{\begin{matrix}\\x=0\text{, }&\text{unconditionally}\\x\in \mathrm{R}\text{, }&R=200\text{ or }R=0\end{matrix}\right.$
$\left\{\begin{matrix}\\R=200\text{; }R=0\text{, }&\text{unconditionally}\\R\in \mathrm{C}\text{, }&x=0\end{matrix}\right.$
$\left\{\begin{matrix}\\R=200\text{; }R=0\text{, }&\text{unconditionally}\\R\in \mathrm{R}\text{, }&x=0\end{matrix}\right.$