I am trying to understand how eq. (1) is simplified to eq. (2), but not getting it clearly.
$ U_P(X,P) = \sum_{j}p_{cj}+\sum_i \sum_j x_{ij}p_{ij} -\psi \sum_i \sum_j \sum_{m \in \mathcal{B}} x_{ij}p_{ij}|g_{jm}|^2$ ---(1)
$ U_P(X,P) = p_{cj}+ (1 -\sum_{m \in \mathcal{B}} \psi x_{ij}|g_{jm}|^2) p_{ij} $ ---(2)
Also, there is a constraint that $ \sum_j x_{ij} =1 $.
I am not getting how the summation in eq. (1) got disappeared in eq. (2).
Any help in this regard will be highly appreciated.