TeX source:

\Delta_m[j] \triangleq \dfrac{\sum_{i=1}^m D(C_i,b,K_s)\vec{T}_i[j]}{\sum_{i=1}^m D(C_i,b,K_s)} - \dfrac{\sum_{i=1}^m [1-D(C_i,b,K_s)]\vec{T}_i[j]}{\sum_{i=1}^m [1-D(C_i,b,K_s)]},