Exams › JEE Main › Maths
If P = [ [1, α, 3], [1, 3, 3], [2, 4, 4] ] is the adjoint of a 3 × 3 matrix A and |A| = 4, then α is equal to:
- 4
- 11
- 5
- 0
Correct answer: 11
Solution
Since P = adj(A) for a 3x3 matrix, |P| = |A|^2 = 4^2 = 16. Expanding det(P) gives 2*alpha - 6 = 16, so alpha = 11.
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