The perturbation theory for the Drazin inverse and its applications Original Research Article

Let A and E be n × n matrices and B = A + E. Denote the Drazin inverse of A by AD. We give an upper bound for the relative error short parallelBD − ADshort parallel/short parallelADshort parallel under certain circumstances. An error bound for the solution for the singular equations Ax = b [b set membership, variant R(A)] is also considered.