Question Details

If A = [ 0 0 3 0 3 0 3 0 0 ] , then - adj A is equal to

Options

A

3

B

9

C

27

D

81

Show Answer

Correct Answer :

Option C

27

Solution :

The correct answer is 27.

Step-by-step Explanation:
First, let us clarify the notation. The expression printed as -adjA represents the determinant of the adjoint of matrix A, which is denoted by |adjA|.

The given matrix A is:
A = [ 0 0 3 0 3 0 3 0 0 ]

Step 1: Find the determinant of matrix A (denoted as |A|)
We expand the determinant along the first row:
| A | = 0 | 3 0 0 0 | - 0 | 0 0 3 0 | + 3 | 0 3 3 0 |

Simplifying the terms:
| A | = 0 - 0 + 3 ( 0 - ( 3 3 ) )
| A | = 3 ( - 3 ) = - 3 3

Step 2: Apply the property of the determinant of an adjoint matrix
For any square matrix A of order n, the determinant of its adjoint is given by:
| adj A | = | A | n - 1

Since A is a 3×3 matrix, its order is n=3.
Therefore:
| adj A | = | A | 3 - 1 = | A | 2

Step 3: Calculate the final value
Substitute the value of |A| into the equation:
| adj A | = ( - 3 3 ) 2
| adj A | = ( - 3 ) 2 ( 3 ) 2 = 9 3 = 27

Thus, the value of the determinant is 27.

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