(2+3i) + (-4+5i)

(2+3i) + (-4+5i)

$$\small{\text{$(2+3i) = \left( \begin{array}{c} 2 \\ 3 \end{array} \right)$}}\\
\small{\text{$(-4+5i) = \left( \begin{array}{c} -4 \\ 5 \end{array} \right)$}}\\
\small{\text{$(2+3i) + (-4+5i) = \left( \begin{array}{c} 2 \\ 3 \end{array} \right)+\left( \begin{array}{c} -4 \\ 5 \end{array} \right)
$}}\\
\small{\text{$=\left( \begin{array}{c} 2-4 \\ 3+5 \end{array} \right) $}}\\
\small{\text{$=\left( \begin{array}{c} -2 \\ 8 \end{array} \right) = (-2+8i)$}}\\$$

(2+3i) + (-4+5i)

=2+3i + -4+5i

=2+3i -4+5i

=-2+8i