THE INVERSE OF OPERATOR MATRIX A WHERE A≥I

Let H and K be Hilbert spaces and let H K be the cartesian product of them.Let B(H),B(K),B(H K),B(K,H),B(H,K) be the Banach spaces of bounded(continuous) operators on H,K,H K,and from K into H and from H into K respectively. In this paper we find the inverse of operator matrix