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If \(A=\left[\begin{array}{lll}1 & 0 & 0 \\ 0 & 0 & 1 \\ 0 & 1 & 0\end{array}\right]\), then the absolute value of the determinant of \(\left(A^{9}+A^{6}+A^{3}+A\right)\) is

Question and options

If A=[100001010]A=\left[\begin{array}{lll}1 & 0 & 0 \\ 0 & 0 & 1 \\ 0 & 1 & 0\end{array}\right], then the absolute value of the determinant of (A9+A6+A3+A)\left(A^{9}+A^{6}+A^{3}+A\right) is
  1. 8
  2. 32
  3. 64
  4. 0

Answer and explanation

Correct answer: B - 32

The absolute determinant is 3232. Since A2=IA^2=I, the matrix is I+3AI+3A, with one diagonal entry 44 outside the block (1331)\begin{pmatrix}1&3\\3&1\end{pmatrix}, giving determinant 4(1−9)=−324(1-9)=-32. The value 6464 comes from replacing the odd powers of AA by II as well.

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