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Let S = left| m in Z : A^m^2 + A^m = 3I - A^-6 right| , where A = beginbmatrix 2 & -1 \\ 1 & 0 endbmatrix . Then n(S) is equal to

Numerical Answer Type:
Enter a numerical value Answer: 2 +4 marks

Solution & Explanation

### Related Formula textInductive formulation for exponent powers of a pattern matrix ### Core Logic Evaluate lower power forms of A to establish inductive sequence patterns: A = beginbmatrix 2 & -1 \\ 1 & 0 endbmatrix, quad A^2 = beginbmatrix 3 & -2 \\ 2 & -1 endbmatrix, quad A^3 = beginbmatrix 4 & -3 \\ 3 & -2 endbmatrix This cleanly establishes general power state rule configuration expression: A^m = beginbmatrix m+1 & -m \\ m & -m+1 endbmatrix ### Step 1: Setup Matrix Power Equation Using the pattern, find expressions for terms: A^6 = beginbmatrix 7 & -6 \\ 6 & -5 endbmatrix, quad A^-6 = (A^6)^-1 = beginbmatrix -5 & 6 \\ -6 & 7 endbmatrix Substitute into the targeted equation block: A^m^2 + A^m = 3beginbmatrix 1 & 0 \\ 0 & 1 endbmatrix - beginbmatrix -5 & 6 \\ -6 & 7 endbmatrix = beginbmatrix 8 & -6 \\ 6 & -4 endbmatrix ### Step 2: Equate Corresponding Elements From the bottom-\left entry [2,1]: m^2 + m = 6 implies m^2 + m - 6 = 0 (m+3)(m-2) = 0 implies m = -3, 2 Both integer states satisfy all matrix components seamlessly. Therefore, the number of elements n(S) = 2. ### Pattern Recognition Always calculate first 2–3 matrix powers to spot linear arithmetic trends across specific cell values (m+1, -m), avoiding tedious full Cayley-Hamilton character expansions. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 12 Mathematics: Matrices

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