JEE MainMathematicsMatrices and DeterminantsMCQ+4 / −1
Let . If , then is equal to :
- A9
- B8
- C10
- D12
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Correct answer: C
- Use the determinant formula for adjugate
For an matrix ,
Here, the matrix is , so
Also, for a scalar multiple:
- First compute
Given
Expand along the first row:
Now,
and
So,
Hence,
- Apply adjugate repeatedly
Let
Then
Now define
We need
Since each time for a matrix,
we get:
- First adjugate:
- Second adjugate:
- Third adjugate:
Thus,
- Express in the form
Since
we have
Therefore,
- Check with options
Option is correct.
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