$$(x+2)(x-3)=x^{2}-kx-6$$
$\left\{\begin{matrix}\\k=1\text{, }&\text{unconditionally}\\k\in \mathrm{C}\text{, }&x=0\end{matrix}\right.$
$\left\{\begin{matrix}\\x=0\text{, }&\text{unconditionally}\\x\in \mathrm{C}\text{, }&k=1\end{matrix}\right.$
$\left\{\begin{matrix}\\k=1\text{, }&\text{unconditionally}\\k\in \mathrm{R}\text{, }&x=0\end{matrix}\right.$
$\left\{\begin{matrix}\\x=0\text{, }&\text{unconditionally}\\x\in \mathrm{R}\text{, }&k=1\end{matrix}\right.$