一类2×2分块矩阵的Drazin逆

he representations for the Drazin inverse of a 2×2 block matrix \\[ M = \\left( {\\begin{array}{*{20}c} A & B \\\ C & 0 \\\\\end{array}} \\right) \\] has been recently studied by N. Castro-González, E. Dopazo, J. Robles, under the assumptions A=B=I, A=I and \\[ CAA^D = C \\]、 \\[ BCA^D = A^D BC \\] respectively. In this paper, we discuss the Drazin inverse of M when A is idempotent, using the methods of block factorization and row and column transposition to M, then transform M to a block matrix which can be easily obtained its representations for the Drazin inverse, and give the representations for the Drazin inverse of M under some new conditions, our results extend some known results on Drazin inverse.