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Let mathrmA = left[mathbfa_mathrmijright] = beginbmatrix log_5128 & log_45 \\ log_58 & log_425 endbmatrix . If A_ij is the cofactor of a_ij , C_ij = sum_k=1^2 a_ik A_jk , 1 leq i, j leq 2 , and C = [C_ij] , then 8|C| is equal to:

Solution & Explanation

### Related Formula sum_k a_ik A_jk = delta_ij |A| implies C = beginbmatrix |A| & 0 \\ 0 & |A| endbmatrix implies |C| = |A|^2 ### Core Logic Evaluate the determinant of matrix A: |A| = (log_5 128)(log_4 25) - (log_4 5)(log_5 8) Using change of base rules: |A| = left(7log_5 2right)left(2log_4 5right) - left(frac12log_2 5right)left(3log_5 2right) |A| = 14left(log_5 2 cdot frac12log_2 5right) - frac32 = 7 - 1.5 = 5.5 = frac112 ### Step 1: Compute |C| and evaluate response target Since matrix properties dictate |C| = |A|^2: |C| = left(frac112right)^2 = frac1214 Evaluate targeted multiplier: 8|C| = 8 times frac1214 = 2 times 121 = 242 ### Pattern Recognition Recognize the core cofactor theorem identity instantly: multiplying rows by cofactors of other rows creates zero elements, yielding basic diagonal scalar structures matching matrix attributes. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 12 Mathematics: Matrices and Determinants

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