JEE Mains · Maths · STD 12 - 3 and 4 . metrices and determinant
Let \(A\) be a \(3 \times 3\) matrix such that
\(\begin{aligned}
& |\operatorname{adj}(\operatorname{adj}(\operatorname{adj} \mathrm{A}))|=81 . \text { If } \\
& \mathrm{S}=\left\{\mathrm{n} \in \mathbb{Z}:(|\operatorname{adj}(\operatorname{adj} A)|)^{\frac{(n-1)^2}{2}}=|A|^{\left(3 n^2-5 n-4\right)}\right\}
\end{aligned}\)
, then \(\sum_{n \in S}\left|A^{\left(n^2+n\right)}\right|\) is equal to
- A 866
- B 750
- C 820
- D 732
Answer & Solution
Correct Answer
(D) 732
Step-by-step Solution
Detailed explanation
\begin{aligned} & |\operatorname{adj}(\operatorname{adj})(\operatorname{adjA})|=81 \\ & \Rightarrow|\operatorname{adjA}|^4=81 \\ & \Rightarrow|\operatorname{adjA}|=3 \\ & \Rightarrow|\mathrm{~A}|^2=3 \\ & \Rightarrow|\mathrm{~A}|=\sqrt{3} \\ &…
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