“…For a nonnegative integer , if rank( 푙+1 ) = rank( 푙 ), then is called the index of and ind( ) = . In recent years, the generalized inverse has been applied in many fields of engineering and technology, such as control [1], the least squares problem [2,3], matrix decomposition [4], image restoration, statistics (see [5]), and preconditioning [6][7][8]. In particular, {2}-inverse plays an important role in stable approximations of ill-posed problems (see [1,9]) and in linear and nonlinear problems [6,10].…”