$\left\{\begin{matrix}a=\frac{cx+d-b}{x}\text{, }&x\neq 0\\a\in \mathrm{C}\text{, }&b=d\text{ and }x=0\end{matrix}\right.$

$\left\{\begin{matrix}a=\frac{cx+d-b}{x}\text{, }&x\neq 0\\a\in \mathrm{R}\text{, }&b=d\text{ and }x=0\end{matrix}\right.$

$b=cx-ax+d$