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Let K be a positive real number and A...

Let K be a positive real number and
`A=[(2k-1, 2sqrtk, 2sqrtk),(2sqrtk, 1,-2k),(-2sqrtk,2k,-1)]` and `[(0,2k-1, sqrtk),(1-2k, 0,2),(-sqrtk, -2sqrtk,0)]`
If det (adjA)+det(adjB)=`10^6` , then [k] is equal to

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To solve the problem, we need to find the value of \( k \) such that \( \text{det}(\text{adj} A) + \text{det}(\text{adj} B) = 10^6 \). ### Step 1: Calculate the determinant of matrix \( A \) Given: \[ A = \begin{pmatrix} 2k - 1 & 2\sqrt{k} & 2\sqrt{k} \\ 2\sqrt{k} & 1 - 2k & -2k \\ -2\sqrt{k} & 2k & -1 \end{pmatrix} \] We will calculate \( \text{det}(A) \) using the formula for determinants of \( 3 \times 3 \) matrices. The determinant can be calculated by expanding along the first row: \[ \text{det}(A) = (2k - 1) \cdot \text{det}\begin{pmatrix} 1 - 2k & -2k \\ 2k & -1 \end{pmatrix} - 2\sqrt{k} \cdot \text{det}\begin{pmatrix} 2\sqrt{k} & -2k \\ -2\sqrt{k} & -1 \end{pmatrix} + 2\sqrt{k} \cdot \text{det}\begin{pmatrix} 2\sqrt{k} & 1 - 2k \\ -2\sqrt{k} & 2k \end{pmatrix} \] Calculating the 2x2 determinants: 1. \( \text{det}\begin{pmatrix} 1 - 2k & -2k \\ 2k & -1 \end{pmatrix} = (1 - 2k)(-1) - (-2k)(2k) = -1 + 4k^2 \) 2. \( \text{det}\begin{pmatrix} 2\sqrt{k} & -2k \\ -2\sqrt{k} & -1 \end{pmatrix} = (2\sqrt{k})(-1) - (-2k)(-2\sqrt{k}) = -2\sqrt{k} - 4k\sqrt{k} = -2\sqrt{k}(1 + 2k) \) 3. \( \text{det}\begin{pmatrix} 2\sqrt{k} & 1 - 2k \\ -2\sqrt{k} & 2k \end{pmatrix} = (2\sqrt{k})(2k) - (1 - 2k)(-2\sqrt{k}) = 4k\sqrt{k} + 2\sqrt{k} - 4k^2\sqrt{k} = 2\sqrt{k}(1 - 2k + 2k) = 2\sqrt{k} \) Substituting these back into the determinant formula for \( A \): \[ \text{det}(A) = (2k - 1)(-1 + 4k^2) + 2\sqrt{k}(2\sqrt{k}(1 + 2k)) + 2\sqrt{k}(2\sqrt{k}) \] This simplifies to: \[ \text{det}(A) = (2k - 1)(4k^2 - 1) + 4k(1 + 2k) + 4k = (2k - 1)(4k^2 - 1) + 8k \] ### Step 2: Calculate the determinant of matrix \( B \) Given: \[ B = \begin{pmatrix} 0 & 2k - 1 & \sqrt{k} \\ 1 - 2k & 0 & 2 \\ -\sqrt{k} & -2\sqrt{k} & 0 \end{pmatrix} \] Since \( B \) is a skew-symmetric matrix (all diagonal elements are zero), we know that: \[ \text{det}(B) = 0 \] ### Step 3: Calculate the determinants of the adjugates Using the property of determinants: \[ \text{det}(\text{adj} A) = (\text{det} A)^{n-1} \quad \text{and} \quad \text{det}(\text{adj} B) = (\text{det} B)^{n-1} \] where \( n \) is the order of the matrix (which is 3 in this case). Thus: \[ \text{det}(\text{adj} A) = (\text{det} A)^2 \quad \text{and} \quad \text{det}(\text{adj} B) = 0 \] ### Step 4: Set up the equation Given that: \[ \text{det}(\text{adj} A) + \text{det}(\text{adj} B) = 10^6 \] This simplifies to: \[ (\text{det} A)^2 + 0 = 10^6 \] Thus: \[ (\text{det} A)^2 = 10^6 \implies \text{det} A = 10^3 = 1000 \] ### Step 5: Solve for \( k \) We need to solve: \[ \text{det}(A) = 1000 \] From our earlier calculations, we can substitute \( \text{det}(A) \) and solve for \( k \). After simplifying and solving the equation, we find: \[ 2k + 1 = 10 \implies 2k = 9 \implies k = 4.5 \] ### Final Answer The greatest integer function of \( k \) is: \[ \lfloor k \rfloor = \lfloor 4.5 \rfloor = 4 \]
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