\begin{gather} % Use gather environment for centering each line
% --- Line 1: A = [Impact x Reach] ---
\text{Artı Değer}(t) =
\Biggl[
\underbrace{
\biggl(
\text{Potansiyel} \times \bigl(\text{Zaman}(t) + \text{Dikkat}(t)\bigr)^{\alpha} \times e^{-\beta\,\bigl(\text{Zaman}(t) + \text{Dikkat}(t)\bigr)}
\biggr)
}_{\text{Etki}
}
\times
\underbrace{
\Biggl( R_{\text{max}} \frac{\bigl(\text{İlişkiler}(t)\bigr)^{\gamma}}{K_R^{\gamma} + \bigl(\text{İlişkiler}(t)\bigr)^{\gamma}} \Biggr)
\times
\Biggl( 1 + \lambda_{\text{erişim}} \int_{0}^{t} e^{-k_{\text{erişim}}(t-\tau)} \text{Erişim}(\tau) \,d\tau \Biggr)
}_{\text{Erişim}}
\Biggr]
\notag \\ % Use \notag if you don't want an equation number here
% --- Line 2: x [Birikim] ---
\times
\Biggl(
1
+
\underbrace{
\lambda_{\text{birikim}}
\int_{0}^{t}
e^{-k_{\text{birikim}}(t-\tau)}
\max\!\bigl\{0,\;\text{Artı Değer}(\tau)\bigr\}
\,d\tau
}_{\text{Geçmiş birikim}}
\Biggr)
\notag % Use \notag if you don't want an equation number here
% --- Line 3: - [Cost] ---
-\;
\frac{
\text{Zaman}(t) + \text{Dikkat}(t)
}{
1
+
\underbrace{
\lambda_{\text{deneyim}}
\int_{0}^{t}
e^{-k_{\text{deneyim}}(t-\tau)}
\bigl( \text{Zaman}(\tau) + \text{Dikkat}(\tau) \bigr)
\,d\tau}_{\text{Geçmiş deneyim}}
}
\end{gather}