試題詳解

10. Let P ∈ be the orthogonal projection matrix, with respect to the Euclidean inner
product, of vectors in onto col( A ) for some nonzero matrix A ∈ . Which of the
following statements is/are true?
(A) ≥rank(P).
(B) P can have an eigenvalue larger than 2.
(C) Px≠ x for all x e .
(D) If k ＜ n and ! e , the system of linear equations Ax = o has a unique least squares
solution.

(E) None of the above is true.