Answer: det(A) is not zero.
- A B = 0
- B A is symmetric
- C All eigenvalues are positive
- D det(A) is not zero
Correct answer: D. det(A) is not zero
Explanation: Cramer's rule applies and gives a unique solution only when det(A) is not zero (A is non-singular). If det(A) = 0, the system is either inconsistent or has infinitely many solutions.
Concept context
Evaluation of determinants, cofactors, adjoint, inverse of matrix, Cramer's rule and area applications. Always in board and JEE.