can this be removed ??

[ sign(z)(|z| - \gamma)_{+} = ] (6)

[ \frac{1} {N} \sum_{i=1}^N x_{ij}(y_i - \tilde{y}i^{(j)}) = \frac {1} {N} \sum{i=1}^N x_{ij} r_i + \tilde{\beta}_j ] (8)

[ \sum_{i=1}^N x_{ij} r_i = (x_j,y) - \sum_{k:|\tilde{\beta}_k | greater 0 }} (x_j, x_k) \tilde{\beta}_k ] (9)