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If B = ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎣ ⎡ − α α 1 3 1 2 0 1 2 5 is the inverse of a 3 × 3 matrix A, then the sum of all values of α for which det(A) + 1 = 0, is :

1. 2
2. – 1
3. 0
4. 1

Correct answer: 1

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