Cho các số phức ${{z}_{1}}\not{=}0, {{z}_{2}}\not{=}0$ thỏa mãn...

$\Leftrightarrow \left[ \begin{aligned}
& \dfrac{{{z}_{1}}}{{{z}_{2}}}=-1-i \\
& \dfrac{{{z}_{1}}}{{{z}_{2}}}=-1+i \\
\end{aligned} \right.$$\Rightarrow \left| \dfrac{{{z}_{1}}}{{{z}_{2}}} \right|=\sqrt{2} \left| \dfrac{{{z}_{2}}}{{{z}_{1}}} \right|=\dfrac{1}{\left| \dfrac{{{z}_{1}}}{{{z}_{2}}} \right|}=\dfrac{1}{\sqrt{2}} \Rightarrow P=\sqrt{2}+\dfrac{1}{\sqrt{2}}=\dfrac{3\sqrt{2}}{2}$.