<正>1引言设Cn×n为n×n复矩阵的集合,对A∈Cn×n,满足rank(Ak+1)=rank(Ak)的最小非负整数k称为A的指标,记为Ind(A)=k,则存在唯一矩阵AD∈Cn×n,满足下列矩阵方程组[1]:
In this paper we study the Drazin inverse of a sum of complex matrices A, B. We express (A+B)D as a function of A, B, AD and BD under the assumptions ABD = O, Bπ BAD = O, Bπ Aπ AB = Bπ AπBA and get some corollaries.