A matrix A has an INVERSE if and only if:
A$\det(A) \neq 0$ (non-singular matrix)
B$\det(A) = 0$ (singular matrix)
C$A$ is square (regardless of det)
D$A$ is symmetric only
Answer & Solution
Correct answer: A. $\det(A) \neq 0$ (non-singular matrix)
Inverse A^(-1) exists ⇔ A is square AND non-singular (det A ≠ 0). Formula: A^(-1) = adj(A) / det(A). Singular matrices (det = 0) cannot be inverted.
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