Second, we compute the value for $f_t$, the activation of the memory cells’ forget gates at time t :
(3)$f_t =\sigma(W_f x_t + U_f h_{t-1}+ b_f)$
\begin{equation}
f_t = \sigma(W_f x_t + U_f h_{t-1} + b_f)
\end{equation}
\framebreak
Given the value of the input gate activation $i_t$, the forget gate activation $f_t$ and the candidate state value $\widetilde{C_t}$, we can compute $C_t$ the memory cells’ new state at time $t$ :
(4)$C_t = i_t *\widetilde{C_t}+ f_t * C_{t-1}$
\begin{equation}
C_t = i_t * \widetilde{C_t} + f_t * C_{t-1}
\end{equation}
With the new state of the memory cells, we can compute the value of their output gates and, subsequently, their outputs :