Adj ( adj A ) = ( det A )^(n-2) A (ARSLAN's question at Yahoo Answers)

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In summary, if $A$ is an $n\times n$ matrix, then $\mbox{adj}\left(\mbox{adj} A\right)=A(\det A)^{n-2}$.
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Hello ARSLAN,

If $M$ is an invertible $n\times n$ matrix, then $M^{-1}=\dfrac{1}{\det M}\mbox{adj } M$ that is $\mbox{adj } M=(\det M)M^{-1}$.

Using well known properties ($\det (aM)=a^n\det M$, $(aM)^{-1}=a^{-1}M^{-1}$ etc):
$$\mbox{adj } \left(\mbox{adj }A \right)=\mbox{adj } \left((\det A)A^{-1}\right)=\det\left((\det A)A^{-1}\right)\cdot\left((\det A)A^{-1}\right)^{-1}\\\left((\det A)^n\cdot\frac{1}{\det A}\right)\cdot\left(\frac{1}{\det A}\cdot (A^{-1})^{-1}\right)=(\det A)^{n-2}A$$
 

Related to Adj ( adj A ) = ( det A )^(n-2) A (ARSLAN's question at Yahoo Answers)

1. What is the purpose of the equation "Adj ( adj A ) = ( det A )^(n-2) A (ARSLAN's question at Yahoo Answers)"?

The equation is used to calculate the adjugate of a matrix A by using its determinant and the matrix itself. The adjugate is a matrix that represents the transpose of the cofactor matrix of A, and it is useful in solving systems of linear equations and finding the inverse of a matrix.

2. How is the adjugate of a matrix calculated?

The adjugate of a matrix A is calculated by taking the transpose of the cofactor matrix of A. The cofactor matrix is formed by replacing each element of A with its corresponding cofactor, which is the determinant of the submatrix formed by removing the row and column of that element. The transpose of the cofactor matrix is then the adjugate of A.

3. What is the significance of the (n-2) power in the equation?

The (n-2) power represents the dimension of the matrix A. This power is necessary to ensure that the dimensions of the adjugate matrix match the dimensions of the original matrix A. This is important because the adjugate matrix is used in operations such as finding the inverse of A, and the dimensions must match for these operations to be valid.

4. Can the equation be used for non-square matrices?

No, the equation can only be used for square matrices. This is because the adjugate matrix can only be calculated for square matrices, and the dimensions of the original matrix and its adjugate must match for the equation to be valid.

5. What is the difference between the adjugate and inverse of a matrix?

The adjugate of a matrix is a matrix itself, while the inverse of a matrix is a scalar value. The inverse of a matrix represents the reciprocal of the determinant of the matrix multiplied by the adjugate of the matrix. In other words, the inverse of a matrix is a scalar value that, when multiplied by the original matrix, yields the identity matrix.

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