Determinant of a compound expression

Let AA and BB be 3×33\times3 matrices with det⁡(A)=3\det(A)=3 and det⁡(B)=2\det(B)=2. Compute det⁡ ⁣(A2 B−1 A⊤)\det\!\big(A^{2}\,B^{-1}\,A^{\top}\big). Give a decimal to two places.

Show hints (2)+
  1. Push det⁡\det through: det⁡(XY)=det⁡Xdet⁡Y\det(XY)=\det X\det Y, det⁡(X−1)=1/det⁡X\det(X^{-1})=1/\det X, det⁡(X⊤)=det⁡X\det(X^{\top})=\det X.
  2. det⁡(A2)=9\det(A^2)=9, det⁡(B−1)=1/2\det(B^{-1})=1/2, det⁡(A⊤)=3\det(A^{\top})=3.

Answer

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13.5 (± 0.001)

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