ตอบข้อ 4.
$Z_{1} = \frac{1}{Z_{1}^{-1}} \ =\ \displaystyle {\frac{1}{\frac{3}{5}-\frac{4}{5}i}}\ =\ \displaystyle ({\frac{1}{\frac{3}{5}-\frac{4}{5}i}})({\frac{\frac{3}{5}+\frac{4}{5}i}{\frac{3}{5}+\frac{4}{5}i}}) \ =\ \frac{3}{5}+\frac{4}{5}i$
และ $2Z_{2} \ =\ 5 - 5Z_{1}$
จะได้ $Z_{2} \ =\ 1-2i$ ดังนั้น $\overline{Z_{2}} \ =\ 1+2i$