$$A = 4 B A$$
$\left\{\begin{matrix}\\A=0\text{, }&\text{unconditionally}\\A\in \mathrm{R}\text{, }&B=\frac{1}{4}\end{matrix}\right.$
$\left\{\begin{matrix}\\B=\frac{1}{4}\text{, }&\text{unconditionally}\\B\in \mathrm{R}\text{, }&A=0\end{matrix}\right.$
