On peut utiliser `split` de l'extension `amsmath`
\begin{equation}
\begin{split}
\begin{split} F = \{F_{x} \in F_{c} &: (|S| > |C|) \\
&\quad \cap (\text{minPixels} < |S| < \text{maxPixels}) \\
&\quad \cap (|S_{\text{conected}}| > |S| - \epsilon) \}
\frac{1}{\sqrt{(x-A)^2+(y-B)^2+(z-C)^2}}&=\\
\frac{1}{D}\sum_{n=0}^\infty\left(\frac{\rho}{D}\right)^n&P_n\left(\frac{Ax+By+Cz}{D\rho}\right),
\end{split} \end{split}
\end{equation}