If A is any n×n matrix, let (r)A denote the r×r submatrix in the upper left corner of A; that is, (r)A is the matrix obtained from A by deleting the las...If A is any n×n matrix, let (r)A denote the r×r submatrix in the upper left corner of A; that is, (r)A is the matrix obtained from A by deleting the last n−r rows and columns. UTU=(UT1D−12)(D−12U1)=UT1(D22)−1U1=(UT1D−11)U1=(L−11)U1=A