Question

If A and B are 3×3 invertible matrices, such that det(A)=2, det(B) =-2. Then det (ABA^T) = ???

Matrices
ANSWERED
asked 2020-11-07

If A and B are 3×3 invertible matrices, such that det(A)=2, det(B) =-2. Then det\( (ABA^T) = ???\)

Expert Answers (1)

2020-11-08

Step 1
To solve this problem, we use the standard result of matrix
Ans: We know that
\(det(A \cdot B)= det(A) \cdot det(B)\)
and
\(det(A)=det(A^T)\)
Step 2
Ans : Given that \(det(A)=2, det(B)=-2\)
\(det(ABA^T)=det(A) \cdot det(BA^T) \ \ \ \left\{det(A \cdot B)=det(A) \cdot det(B)\right\}\)
\(=det(A) \cdot det(B) \cdot det(A^T) \ \ \ \left\{det(A)=det(A^T)\right\}\)
\(=det(A) \cdot det(B) \cdot det(A)\)
\(=2 \cdot (-2) \cdot 2\)
\(det(ABA^T)=-8\)

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