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থিম নির্বাচন

আপনার পছন্দের থিম বেছে নিন।

যদি \( A = \begin{bmatrix} -1 & -3 \\ 2 & 4 \end{bmatrix} \) হয়, তাহলে \( | \text{Adj}(A) | \) কত হবে?

A. 10
B. 1000
C. 100
D. 110
সঠিক উত্তরঃ B. 1000
Another Explanation (5):
Given matrix \( A = \begin{bmatrix} -1 & -3 \\ 2 & 4 \end{bmatrix} \)

Step 1: Find \( \det(A) \)
\[
\det(A) = (-1)(4) - (-3)(2) = -4 + 6 = 2
\]

Step 2: Find \( \text{Adj}(A) \)
\[
\text{Adj}(A) = (\det(A)) \times A^{-1}
\]
But more straightforwardly, for a 2x2 matrix:
\[
\text{Adj}(A) = \begin{bmatrix} d & -b \\ -c & a \end{bmatrix}
\]
where \( A = \begin{bmatrix} a & b \\ c & d \end{bmatrix} \)

So,
\[
a = -1, \quad b = -3, \quad c = 2, \quad d = 4
\]
\[
\text{Adj}(A) = \begin{bmatrix} 4 & 3 \\ -2 & -1 \end{bmatrix}
\]

Step 3: Find \( |\text{Adj}(A)| \)
\[
|\text{Adj}(A)| = (4)(-1) - (3)(-2) = -4 + 6 = 2
\]

**Note:** The problem asks for \( |\text{Adj}(A)| \), but the answer provided is 1000, which suggests there might be a different interpretation or typo.

Alternatively, considering the relation:
\[
\text{For a 2x2 matrix } A, \quad |\text{Adj}(A)| = |\det(A) \times A^{-1}| = |\det(A)|^2
\]
since \( |\text{Adj}(A)| = |\det(A)|^{n-1} \) for an \( n \times n \) matrix, and in 2x2:
\[
|\text{Adj}(A)| = |\det(A)|^{2-1} = |\det(A)| = 2
\]

But this conflicts with the earlier calculation.

Alternatively, for any invertible matrix:
\[
\text{Adj}(A) = (\det A) \times A^{-1}
\]
and the determinant of \( \text{Adj}(A) \) is:
\[
|\text{Adj}(A)| = |\det A|^{n-1} \times |\det A| = |\det A|^{n}
\]
for an \( n \times n \) matrix, so in 2x2:
\[
|\text{Adj}(A)| = |\det A|^{2} = 2^{2} = 4
\]

This aligns with the standard property:
\[
|\text{Adj}(A)| = |\det(A)|^{n-1}
\]
for \( n \times n \) matrices.

Hence, the correct calculation:
\[
|\text{Adj}(A)| = |\det(A)|^{2-1} = |\det(A)| = 2
\]

But the provided answer is 1000, which suggests the problem expects the calculation:
\[
|\text{Adj}(A)| = |\det(A)|^{n-1} \times |\det(A)| = |\det(A)|^{n} = 2^{2} = 4
\]

Given the inconsistency, perhaps the intention is:
\[
|\text{Adj}(A)| = |\det(A)|^{n-1} \times |\det(A)| = |\det(A)|^{n} = 2^{2} = 4
\]

Yet, the answer is 1000, which is \( 10^3 \). Suppose the eigenvalues or specific calculations lead to that.

Alternatively, considering the general property:
\[
|\text{Adj}(A)| = |\det(A)|^{n-1}
\]
for an \( n \times n \) matrix.

In this case, \( |\det(A)| = 2 \), so:
\[
|\text{Adj}(A)| = 2^{2-1} = 2
\]

Since the answer is given as 1000, perhaps the question involves the matrix \( A \) scaled or different.

**Final conclusion:**

Given the data and standard properties, the most consistent calculation yields:


|Adj(A)| = |\det(A)|^{n-1} = 2^{1} = 2


But since the user states the answer is "1000," perhaps they are considering:

\[
| \text{Adj}(A)| = |\det(A)|^{n} = 2^{2} = 4
\]

or a different interpretation.

**Therefore, the formal mathematical answer is:**


|Adj(A)| = |\det(A)|^{n-1} = 2^{2-1} = 2