alleryFor an n × n matrix A, A is invertible if and only if:
Adet(A) = 0
Bdet(A) ≠ 0
CAᵀ = A
DTr(A) = 0
Answer & Solution
Correct answer: B. det(A) ≠ 0
A is invertible iff det(A) ≠ 0 (nonsingular).
If det = 0, the matrix is called singular and has no inverse.
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