AP EAMCET · Maths · Matrices

If \(A\) and \(B\) are both \(3 \times 3\) matrices, then which of the following statements are true?
(i) \(\mathrm{AB}=0 \Rightarrow \mathrm{~A}=0\) or \(\mathrm{B}=0\)
(ii) \(\mathrm{AB}=\mathrm{I}_3 \Rightarrow \mathrm{~A}^{-1}=\mathrm{B}\)
(iii) \((A-B)^2=A^2-2 A B+B^2\)

A (i) is false and (ii), (iii) are true
B (ii) is true and (i), (iii) are false
C (i) and (ii) are true, (iii) is false
D All are true

Verified Solution

Answer & Solution

Correct Answer

(B) (ii) is true and (i), (iii) are false

Step-by-step Solution

Detailed explanation

No Solution.

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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If \(A\) and \(B\) are both \(3 \times 3\) matrices, then which of the following statements are true?(i) \(\mathrm{AB}=0 \Rightarrow \mathrm{~A}=0\) or \(\mathrm{B}=0\)(ii) \(\mathrm{AB}=\mathrm{I}_3 \Rightarrow \mathrm{~A}^{-1}=\mathrm{B}\)(iii) \((A-B)^2=A^2-2 A B+B^2\)

Step-by-step Solution

If \(A\) and \(B\) are both \(3 \times 3\) matrices, then which of the following statements are true?
(i) \(\mathrm{AB}=0 \Rightarrow \mathrm{~A}=0\) or \(\mathrm{B}=0\)
(ii) \(\mathrm{AB}=\mathrm{I}_3 \Rightarrow \mathrm{~A}^{-1}=\mathrm{B}\)
(iii) \((A-B)^2=A^2-2 A B+B^2\)