If A = [ ll 0 & 1 1 & 2 ], then adj A will be : - Vidyadip

MCQ

If $A =\left[\begin{array}{ll}0 & 1 \\ 1 & 2\end{array}\right]$, then adj A will be :

✓
$\left[\begin{array}{cc}2 & -1 \\ -1 & 0\end{array}\right]$
B
$\left[\begin{array}{cc}2 & -1 \\ -2 & 0\end{array}\right]$
C
$\left[\begin{array}{cc}2 & -1 \\ -1 & 2\end{array}\right]$
D
$\left[\begin{array}{cc}-2 & -1 \\ -1 & 0\end{array}\right]$

✓

Answer

Correct option: A.

$\left[\begin{array}{cc}2 & -1 \\ -1 & 0\end{array}\right]$

(A)
$A _{11}=2, A_{12}=-1, A_{21}=-1, A_{22}=0$$
\operatorname{adj} A=\left[\begin{array}{ll}
A_{11} & A_{12} \\
A_{21} & A_{22}
\end{array}\right]^{\prime}=\left[\begin{array}{cc}
2 & -1 \\
-1 & 0
\end{array}\right]^{\prime}=\left[\begin{array}{cc}
2 & -1 \\
-1 & 0
\end{array}\right]
$
Hence correct option is (A).

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