A square matrix $A$ is invertible if and only if:
A$A$ is symmetric
B$A$ is of even order
C$|A| = 0$
D$|A| \neq 0$
Answer & Solution
Correct answer: D. $|A| \neq 0$
A is invertible exactly when it is non-singular, i.e. |A| ≠ 0.
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