Question

Express the mentioned below complex number in the standard form $a+ib$.
$\left(i\right)(1+i)(1+2i)$

Answer 1

$\because (1+i)(1+2i)$
$=1+2i+i+2i^2$
$=1+3i+2(-1)\{\because i^2=-1\}$
$=1+3i-2$
$=-1+3i$

$\therefore (1+i)(1+2i)=-1+3i$