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Question: Answered & Verified by Expert
Let for A=123α31112,A=2. If |2adj(2adj(2A))|=32n, then 3n+α is equal to
MathematicsMatricesJEE MainJEE Main 2023 (13 Apr Shift 2)
Options:
  • A 9
  • B 11
  • C 12
  • D 10
Solution:
2253 Upvotes Verified Answer
The correct answer is: 11

Given that A=123α31112

|A|=2

16-1-α-7=2

-α-2=2

α=-4

|2adj(2adj(2A))|=32n

We know that kA=knAadj(adj(A))=An-12 and adjkA=kn-1adjA.

=23|adj(2adj(2A))|

=23|23-1adj(adj(2A))|

=23·(4)3|adj(adj(2A))|

=29|2A|(2)2

=29·|2A|4

=29·212|A|4

=221·24=225=(32)n=(2)5n

n=5

3n+α=15-4=11

Hence this is the correct option.

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