(f_{j+1}|e_i)= \\* =(x_{j+1} - \sum_{k=1}^j (x_{j+1}|e_k)e_k = \\* = (x_{j+1}|e_i) - \sum_{k=1}^j (x_{j+1}|e_k)(e_k|e_i) = \\* = (x_{j+1}|e_i) - (x_{j+1}|e_i) \cdot 1