Class CBSE Class 12 Mathematics Matrices and Determinants Q #764
KNOWLEDGE BASED
APPLY
1 Marks 2025 MCQ SINGLE
If \(A\) and \(B\) are invertible matrices, then which of the following is \underline{not correct}?
(A) \((A + B)^{-1} = B^{-1} + A^{-1}\)
(B) \((AB)^{-1} = B^{-1} A^{-1}\)
(C) \(\text{adj}(A) = |A| A^{-1}\)
(D) \(|A^{-1}| = |A|^{-1}\)
Correct Answer: A

AI Tutor Explanation

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Step-by-Step Solution

  1. Analyze Option A: \((A + B)^{-1} = B^{-1} + A^{-1}\). This statement is generally incorrect. The inverse of a sum of matrices is not the sum of their inverses.
  2. Analyze Option B: \((AB)^{-1} = B^{-1} A^{-1}\). This statement is a fundamental property of invertible matrices and is correct.
  3. Analyze Option C: \(\text{adj}(A) = |A| A^{-1}\). This statement is the definition of the adjoint of a matrix and is correct.
  4. Analyze Option D: \(|A^{-1}| = |A|^{-1}\). This statement is a property of the determinant of an inverse matrix and is correct.
  5. Conclusion: The incorrect statement is Option A.

Correct Answer: \( (A + B)^{-1} = B^{-1} + A^{-1} \)

AI Suggestion: Option A

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Pedagogical Audit
Bloom's Analysis: This is an APPLY question because the student needs to apply the properties of invertible matrices to identify the incorrect statement.
Knowledge Dimension: CONCEPTUAL
Justification: The question requires understanding the concepts of matrix inverses, adjoints, and determinants, rather than just recalling facts.
Syllabus Audit: In the context of CBSE Class 12, this is classified as KNOWLEDGE. The question directly tests knowledge of matrix algebra and properties of inverse matrices as covered in the textbook.