4 Write down the equation of the locus represented in the Argand diagram shown in Fig. 4.
\begin{figure}[h]
\includegraphics[alt={},max width=\textwidth]{35094899-149c-438e-b6c8-b333d2fefc0c-2_474_497_1932_824}
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\caption{Fig. 4}
\end{figure}