Let A be a 3 × 3 real matrix. If det ( 2 Adj ( 2 Adj ( Adj ( 2 A ) ) ) ) = 2 41 , then the value of det…

Let A be a 3×3 real matrix. If det(2Adj(2Adj(Adj(2A))))=241, then the value of detA2 equals ______.

Solution

|KA|=Kn|A|, If A is n×n matrix

|AdjA|=|A|n-1 If A is n×n matrix

|2Adj(2Adj(Adj(2A)))|=241

23|Adj(2Adj(Adj(2 A)))|=241
|Adj(2Adj(Adj(2 A)))|=238
(|2Adj(Adj(2 A))|)2=238
|2Adj(Adj(2 A))|=219
23|Adj(Adj(2 A))|=219
|Adj(Adj(2 A))|=216
(|Adj(2 A)|)2=216
|Adj(2 A)|=28
|(2 A)|2=28
|(2 A)|=24
23| A|=24
|A|=2

So, A2=A2=4

Asked in: JEE Main 2021 (26 Aug Shift 2)

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