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A matrix A is INVERTIBLE if and only if
Adet(A) ≠ 0 (equivalently, A is full rank)
Btr(A) ≠ 0
CA is symmetric
Ddet(A) = 0
Answer & Solution
Correct answer: A. det(A) ≠ 0 (equivalently, A is full rank)
Non-zero determinant ⇔ full column rank ⇔ injective map ⇔ invertible. Trace and symmetry do not characterise invertibility.
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