JEE Mains · Maths · STD 12 - 3 and 4 . metrices and determinant
Let \(A = \begin{bmatrix} 1 & 2 \\ 1 & \alpha \end{bmatrix}\) and \(B = \begin{bmatrix} 3 & 3 \\ \beta & 2 \end{bmatrix}\). If \(A^2 - 4A + I = O\) and \(B^2 - 5B - 6I = O\), then among the two statements :
(S1): \([(B-A)(B+A)]^T = \begin{bmatrix} 13 & 15 \\ 7 & 10 \end{bmatrix}\)
and
(S2): \(\det(\text{adj}(A+B)) = -5\),
- A only (S1) is correct
- B only (S2) is correct
- C both (S1) and (S2) are correct
- D both (S1) and (S2) are wrong
Answer & Solution
Correct Answer
(B) only (S2) is correct
Step-by-step Solution
Detailed explanation
For a \(2 \times 2\) matrix \(M\), the characteristic equation is given by \(M^2 - \text{Tr}(M)M + \det(M)I = O\). For matrix \(A = \begin{bmatrix} 1 & 2 \\ 1 & \alpha \end{bmatrix}\), we are given \(A^2 - 4A + I = O\). Comparing the trace, we get…
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