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Let A and B are square matrices of order...

Let A and B are square matrices of order 2 such that `A+adj(B^(T))=[(3,2),(2,3)] and A^(T)-adj(B)=[(-2,-1),(-1, -1)]`, then `A^(2)+2A^(3)+3A^(4)+5A^(5)` is equal to (where `M^(T)` and adj(M) represent the transpose matrix and adjoint matrix of matrix M respectively and I represents the identity matrix of order 2)

A

4A

B

7A

C

11A

D

10I

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The correct Answer is:
To solve the problem step by step, we will first analyze the given equations involving matrices \( A \) and \( B \). ### Step 1: Set up the equations We are given two equations: 1. \( A + \text{adj}(B^T) = \begin{pmatrix} 3 & 2 \\ 2 & 3 \end{pmatrix} \) 2. \( A^T - \text{adj}(B) = \begin{pmatrix} -2 & -1 \\ -1 & -1 \end{pmatrix} \) ### Step 2: Transpose the second equation Taking the transpose of the second equation: \[ (A^T - \text{adj}(B))^T = \begin{pmatrix} -2 & -1 \\ -1 & -1 \end{pmatrix}^T \] This gives: \[ A - \text{adj}(B)^T = \begin{pmatrix} -2 & -1 \\ -1 & -1 \end{pmatrix} \] ### Step 3: Rearranging the equations From the first equation, we can express \( A \): \[ A = \begin{pmatrix} 3 & 2 \\ 2 & 3 \end{pmatrix} - \text{adj}(B^T) \] From the transposed second equation, we can express \( A \): \[ A = \begin{pmatrix} -2 & -1 \\ -1 & -1 \end{pmatrix} + \text{adj}(B)^T \] ### Step 4: Equating the two expressions for \( A \) Setting the two expressions for \( A \) equal to each other: \[ \begin{pmatrix} 3 & 2 \\ 2 & 3 \end{pmatrix} - \text{adj}(B^T) = \begin{pmatrix} -2 & -1 \\ -1 & -1 \end{pmatrix} + \text{adj}(B)^T \] ### Step 5: Solve for \( \text{adj}(B) \) Rearranging gives: \[ \begin{pmatrix} 3 & 2 \\ 2 & 3 \end{pmatrix} + \begin{pmatrix} 2 & 1 \\ 1 & 1 \end{pmatrix} = \text{adj}(B^T) + \text{adj}(B)^T \] Calculating the left side: \[ \begin{pmatrix} 5 & 3 \\ 3 & 4 \end{pmatrix} = \text{adj}(B^T) + \text{adj}(B)^T \] ### Step 6: Finding \( A \) From the earlier equations, we can find \( A \): \[ A = \begin{pmatrix} 1 & 1 \\ 1 & 1 \end{pmatrix} \] ### Step 7: Calculate \( A^2 \), \( A^3 \), \( A^4 \), and \( A^5 \) Calculating \( A^2 \): \[ A^2 = A \cdot A = \begin{pmatrix} 1 & 1 \\ 1 & 1 \end{pmatrix} \cdot \begin{pmatrix} 1 & 1 \\ 1 & 1 \end{pmatrix} = \begin{pmatrix} 2 & 2 \\ 2 & 2 \end{pmatrix} \] Calculating \( A^3 \): \[ A^3 = A^2 \cdot A = \begin{pmatrix} 2 & 2 \\ 2 & 2 \end{pmatrix} \cdot \begin{pmatrix} 1 & 1 \\ 1 & 1 \end{pmatrix} = \begin{pmatrix} 4 & 4 \\ 4 & 4 \end{pmatrix} \] Calculating \( A^4 \): \[ A^4 = A^3 \cdot A = \begin{pmatrix} 4 & 4 \\ 4 & 4 \end{pmatrix} \cdot \begin{pmatrix} 1 & 1 \\ 1 & 1 \end{pmatrix} = \begin{pmatrix} 8 & 8 \\ 8 & 8 \end{pmatrix} \] Calculating \( A^5 \): \[ A^5 = A^4 \cdot A = \begin{pmatrix} 8 & 8 \\ 8 & 8 \end{pmatrix} \cdot \begin{pmatrix} 1 & 1 \\ 1 & 1 \end{pmatrix} = \begin{pmatrix} 16 & 16 \\ 16 & 16 \end{pmatrix} \] ### Step 8: Calculate \( A^2 + 2A^3 + 3A^4 + 5A^5 \) Now we can compute: \[ A^2 + 2A^3 + 3A^4 + 5A^5 = \begin{pmatrix} 2 & 2 \\ 2 & 2 \end{pmatrix} + 2 \begin{pmatrix} 4 & 4 \\ 4 & 4 \end{pmatrix} + 3 \begin{pmatrix} 8 & 8 \\ 8 & 8 \end{pmatrix} + 5 \begin{pmatrix} 16 & 16 \\ 16 & 16 \end{pmatrix} \] Calculating each term: \[ = \begin{pmatrix} 2 & 2 \\ 2 & 2 \end{pmatrix} + \begin{pmatrix} 8 & 8 \\ 8 & 8 \end{pmatrix} + \begin{pmatrix} 24 & 24 \\ 24 & 24 \end{pmatrix} + \begin{pmatrix} 80 & 80 \\ 80 & 80 \end{pmatrix} \] Adding these matrices together: \[ = \begin{pmatrix} 2 + 8 + 24 + 80 & 2 + 8 + 24 + 80 \\ 2 + 8 + 24 + 80 & 2 + 8 + 24 + 80 \end{pmatrix} = \begin{pmatrix} 114 & 114 \\ 114 & 114 \end{pmatrix} \] ### Final Answer Thus, the final result is: \[ \begin{pmatrix} 114 & 114 \\ 114 & 114 \end{pmatrix} \]
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