Answer
9
Work Step by Step
If A and B are $n×n$ matrices, then:
$\det(AB)=\det(A).\det(B)$
Also: $\det(A^T)=\det(A)$
Hence here,
$\det(B^{-1}AB)^2=\det(A).\det(B)=[\frac{1}{\det(B)}\det(A).\det(B)]^2=[\frac{1}{-4}.3.(-4)]^2=3^2=9$
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