设X,Y为Banach空间,T为从X到Y的线性算子.T的值域R(T)≠Y且为逼近紧子空间,T的零空间N(T)≠{θ}.证得不适定算子方程Tx=y的最佳逼近解对任意y∈Y均存在的充分必要条件是N(T)为X的迫近子空间.
Let X,Y be Banach space, T be linear operator from X to Y. The range of T, R (T) ≠ Y and R(T) is approximation compact sub-space. The null space of T,N(T) ≠ {θ}. We prove that the best approximation solution of ill-posed operator equation Tx = y exists for every y ∈ Y if and only if N(T) is approximation sub-space of X.