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Q55Section I (Objective (Q1–Q80))55 of 80

Linear Algebra — idempotent matrices and generalized inverses

Consider the following statements: I. If A\mathbf{A} is an idempotent matrix, then rank (A)(\mathbf{A}) = Trace (A)(\mathbf{A}). II. Given a matrix A\mathbf{A}, there exists a matrix A−\mathbf{A}^-, with the property AA−A=A\mathbf{AA^-A} = \mathbf{A} and trace (A−A)(\mathbf{A^-A}) = rank (A)(\mathbf{A}). Which of the statements given above is/are correct?

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