Question

Solve with explanation
$A = \left| \begin{array}{ccc} -a & 1 & 1\\ 1 & -a & 1 \\ 1&1&-a \end{array}\right|$, and
$B = \left| \begin{array}{cc} a & 1 \\ 1&a \end{array} \right|$, then what is $\dfrac{dA}{da}$?

(a) 1 + 3B
(b) 3B
(c) -3B
(d)1 - 3B​

Answer 1

First one a 1+3B






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Answer 2

Answer:

1+3B

beacuse

1&1 right/text[ccc]

a & 1 & 1\\ 1 & -a &

=1+3B