Sassini is right but it is not finished
$${\mathtt{9}}{\mathtt{\,-\,}}{\mathtt{12}}{i}{\mathtt{\,\small\textbf+\,}}{\mathtt{4}}\left[{{i}}^{{\mathtt{2}}}\right]$$
= $${\mathtt{9}}{\mathtt{\,-\,}}{\mathtt{12}}{i}{\mathtt{\,-\,}}{\mathtt{4}}$$
= $${\mathtt{5}}{\mathtt{\,-\,}}{\mathtt{12}}{i}$$
.