MHT CET 2022 Mathematics question
If A = and A (adj A) = KI, then the value of K is (where I is unit matrix of order 3)
Answer: (B)
Solution
For any square matrix, , so . Expand along the first row: $|A| = 1(0·0 - (-5)(5)) - 3((-3)(0) - (-5)(2)) + (-2)((-3)(5) - 0·2) = 1(25) - 3(10) + (-2)(-15)
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