$$(a+b)^{3}=a^{3}+b^{3}+3a^{2}b+3ab^{2}b$$
$\left\{\begin{matrix}\\a=0\text{, }&\text{unconditionally}\\a\in \mathrm{C}\text{, }&b=0\text{ or }b=1\end{matrix}\right.$
$\left\{\begin{matrix}\\a=0\text{, }&\text{unconditionally}\\a\in \mathrm{R}\text{, }&b=0\text{ or }b=1\end{matrix}\right.$
$\left\{\begin{matrix}\\b=0\text{; }b=1\text{, }&\text{unconditionally}\\b\in \mathrm{C}\text{, }&a=0\end{matrix}\right.$
$\left\{\begin{matrix}\\b=0\text{; }b=1\text{, }&\text{unconditionally}\\b\in \mathrm{R}\text{, }&a=0\end{matrix}\right.$