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Question: Answered & Verified by Expert
The possible values of scalar k such that the matrix A - 1 - kI is singular where A= 1 0 2 0 2 1 1 0 0 , are
MathematicsDeterminantsJEE Main
Options:
  • A 1 2 ,2
  • B 1, 1 2
  • C 1 2 , 1 2
  • D 1,1
Solution:
1163 Upvotes Verified Answer
The correct answer is: 1, 1 2
A - 1 - kI = 0

A A - 1 - kI = 0 A 0

I - kA = 0

Ik-A=0  A-1k. I=0

A-λI=0, where λ=1k

1 - λ 0 2 0 2 - λ 1 1 0 - λ = 0

1 - λ - λ 2 - λ + 2 0 - 2 - λ = 0

- λ 3 + 3 λ 2 - 2 λ - 4 + 2 λ = 0

λ 3 3 λ 2 +4=0λ=2, 2,1k=1, 1 2

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