複選題
15. (10%) An m x n matrix Xis invertible if
(A) The columns of X span Rm
(B) The reduced row echelon form of X is In
(C) The rows of X are linearly independent
(D) The columns of X are linearly independent
(E) None of the preceding statements is true

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統計： A(0), B(1), C(0), D(0), E(1) #2793054