JEE Mains · Maths · STD 12 - 3 and 4 . metrices and determinant
Let \(A\) be a \(3 \times 3\) matrix such that \(X^T A X=O\) for all nonzero \(3 \times 1\) matrices \(X=\left[\begin{array}{l}x \\ y \\ z\end{array}\right]\). If \(\mathbf{A}\left[\begin{array}{l}1 \\ 1 \\ 1\end{array}\right]=\left[\begin{array}{c}1 \\ 4 \\ -5\end{array}\right], \mathbf{A}\left[\begin{array}{l}1 \\ 2 \\ 1\end{array}\right]=\left[\begin{array}{c}0 \\ 4 \\ -8\end{array}\right]\), and \(\operatorname{det}(\operatorname{adj}(2(\mathbf{A}+\mathbf{1})))-2^\alpha 3^\beta 5^\gamma, \alpha, \beta, \gamma \in N\), then \(\alpha^2+\beta^2+\gamma^2\) is ___.
- A 40
- B 42
- C 44
- D 46
Answer & Solution
Correct Answer
(C) 44
Step-by-step Solution
Detailed explanation
\begin{aligned} & X^{\top} A X=0 \\ & (x y z)\left[\begin{array}{lll} a_1 & a_2 & a_3 \\ b_1 & b_2 & b_3 \\ c_1 & c_2 & c_3 \end{array}\right]\left[\begin{array}{l} x \\ y \\ z \end{array}\right]=0 \\ & (x y z)\left[\begin{array}{l} a_1 x+a_2 y+a_3 z \\ b_1 x+b_2 y+b_3 z \\ c_1…
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