Question Number 23741 by hassaneinsultan last updated on 04/Nov/17
$$\left(\mathrm{1}+{i}\right)\left(\mathrm{2}+{i}\right) \\ $$
Answered by Joel577 last updated on 05/Nov/17
$$=\:\mathrm{2}\:+\:{i}\:+\:\mathrm{2}{i}\:+\:{i}^{\mathrm{2}} \\ $$$$=\:\mathrm{2}\:+\:\mathrm{3}{i}\:−\:\mathrm{1} \\ $$$$=\:\mathrm{1}\:+\:\mathrm{3}{i} \\ $$