Question

Let A be a 3 × 3 real matrix such that det(A) = 6 and
$adj\ A=\begin{pmatrix} 1 & -1 & 2 \\\ 5 & 7 & 1 \\\ -1 & 1 & 1 \end{pmatrix}$
where adj A denotes the adjoint of A.
Then the trace of A equals __________ (round off to 2 decimal places)

Answer 1

The correct answer is 3.45 to 3.55.(approx)