If A = [ * 20 c 1& - 1 2&3 ], then adj A is equal to - Vidyadip

MCQ

If $A = \left[ {\begin{array}{*{20}{c}}1&{ - 1}\\2&3\end{array}} \right]$, then adj $A$ is equal to

A
$\left[ {\begin{array}{*{20}{c}}{ - 3}&{ - 1}\\2&{ - 1}\end{array}} \right]$
✓
$\left[ {\begin{array}{*{20}{c}}3&1\\{ - 2}&1\end{array}} \right]$
C
$\left[ {\begin{array}{*{20}{c}}3&{ - 2}\\1&1\end{array}} \right]$
D
$\left[ {\begin{array}{*{20}{c}}{\,3}&{ - 1}\\{ - 2}&1\end{array}} \right]$

✓

Answer

Correct option: B.

$\left[ {\begin{array}{*{20}{c}}3&1\\{ - 2}&1\end{array}} \right]$

b
(b) adj $(A) $ can be obtained by changing the diagonal element and changing the sign of off diagonal elements.

Here, $adj\,(A) = \left[ {\begin{array}{*{20}{c}}3&1\\{ - 2}&1\end{array}} \right]$.

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