JEE Mains · Maths · STD 12 - 3 and 4 . metrices and determinant
Let \(B=\left[\begin{array}{ccc}1 & 3 & \alpha \\ 1 & 2 & 3 \\ \alpha & \alpha & 4\end{array}\right], \alpha > 2\) be the adjoint of \(a\) matrix \(A\) and \(| A |=2\), then \([\alpha\,\,-2 \alpha \,\, \alpha \,\,] B \left[\begin{array}{c}\alpha \\ -2 \alpha \\ \alpha\end{array}\right]\) is equal to :-
- A \(16\)
- B \(32\)
- C \(-16\)
- D \(0\)
Answer & Solution
Correct Answer
(C) \(-16\)
Step-by-step Solution
Detailed explanation
Given, \(B=\left[\begin{array}{lll}1 & 3 & \alpha \\ 1 & 2 & 3 \\ \alpha & \alpha & 4\end{array}\right]\) \(|B|=4\) \(1(8-3 \alpha)-3(4-3 \alpha)+\alpha(\alpha-2 \alpha)=4\) \(-\alpha^2+6 \alpha-8=0\) \(\alpha=2,4\) Given,\(\alpha > 2\) So,\(\alpha=2\) is rejected…
See the Complete Solution
Get step-by-step explanations for this and 2.5 Lakh+ more JEE, NEET & CET questions.
- Unlock all solutions
- Practice the full chapter
- Track accuracy across PYQs
4.8 rated on Google Play · 14,000+ reviews
More questions from Maths
- The remainder, when \(7^{103}\) is divided by 23 , is equal to :JEE Mains 2025 Medium
- Let \(O\) be the origin and the position vector of \(A\) and \(B\) be \(2 \hat{i}+2 \hat{j}+\hat{k}\) and \(2 \hat{i}+4 \hat{j}+4 \hat{k}\) respectively. If the internal bisector of \(\angle A O B\) meets the line \(A B\) at \(\mathrm{C}\), then the length of \(\mathrm{OC}\) isJEE Mains 2024 Medium
- Let \(p\) and \(q\) be two real numbers such that \(p+q=\) 3 and \(p^{4}+q^{4}=369\). Then \(\left(\frac{1}{p}+\frac{1}{q}\right)^{-2}\) is equal toJEE Mains 2022 Hard
- The mean and variance of \(20\) observations are found to be \(10\) and \(4,\) respectively. On rechecking, it was found that an observation \(9\) was incorrect and the correct observation was \(11\). Then the correct variance isJEE Mains 2020 Hard
- Let \(A=\left(\begin{array}{cc}4 & -2 \\ \alpha & \beta\end{array}\right)\) . If \(A ^{2}+\gamma A +18 I = O\), then \(\operatorname{det}( A )\) is equal toJEE Mains 2022 Easy
- The sum \(\sum\limits_{k=1}^{20}(1+2+3+\ldots+k)\) isJEE Mains 2020 Medium
More PYQs from JEE Mains
- If the equation of the hyperbola with foci \((4,2)\) and \((8,2)\) is \(3 x^2-y^2-\alpha x+\beta y+\gamma=0\), then \(\alpha+\beta+\gamma\) is equal to _____.
JEE Mains 2025 Easy - Let \(y=y(x)\) be solution of the following differential equation \(e^{y} \frac{d y}{d x}-2 e^{y} \sin x+\sin x \cos ^{2} x=0, y\) \(\left(\frac{\pi}{2}\right)=0\). If \(y(0)=\log _{e}\left(\alpha+\beta e^{-2}\right)\), then \(4(\alpha+\beta)\) is equal to \(....\)JEE Mains 2021 Hard
- The maximum value of the function \(f\,(x)\, = 3{x^3} - 18{x^2} + 27x\,\, - 40\) on the set \(S = \{ x\, \in \,R\,:\,{x^2}\, + \,30\, \le \,11x\} \) isJEE Mains 2019 Hard
- Let \(\vec{a}, \vec{b}\) and \(\vec{c}\) be three non-zero vectors such that \(\vec{b}\) and \(\vec{c}\) are non-collinear if \(\vec{a}+5 \vec{b}\) is collinear with \(\overrightarrow{\mathrm{c}}, \overrightarrow{\mathrm{b}}+6 \overrightarrow{\mathrm{c}}\) is collinear with \(\overrightarrow{\mathrm{a}}\) and \(\vec{a}+\alpha \vec{b}+\beta \vec{c}=\overrightarrow{0}\), then \(\alpha+\beta\) is equal toJEE Mains 2024 Medium
- Let \(y = y(x)\) be the solution of the differential equation, \(x\frac{{dy}}{{dx}} + y = x\,{\log _e}\,x,\,\left( {x > 1} \right)\) If \(2y(2) = log_e\, 4 -1\), then \(y(e)\) is equal toJEE Mains 2019 Hard
- The minimum value of the function \(f(x)=\int \limits_0^2 e^{|x-t|} d t\) isJEE Mains 2023 Hard