If A and B are matrices of same order, under what condition is (A + B)² = A² + 2AB + B² true?
If A and B are matrices of same order, under what condition is (A + B)² = A² + 2AB + B² true?
- A. Always
- B. Never
- C. If A = B
- D. If AB = BA
Answer: D) If AB = BA
Explanation: Expanding (A + B)² gives (A + B)(A + B) = A² + AB + BA + B². For this to equal A² + 2AB + B², we must have AB = BA (the matrices commute).
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