Lösung 3.1:1c

Complex numbers satisfy the same rules of arithmetic as ordinary numbers, with the addition that \displaystyle i^2=-1. The distributivity rule gives that

\displaystyle \begin{align}i(2+3i)&=i\cdot 2+i\cdot 3i=2i+3i^2\\ &=2i+3\cdot (-1)=2i-3\\ &=-3+2i\end{align}