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STD 12 - 3 and 4 . determinant and metrices — JEE STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 ScienceJEESTD 12 - 3 and 4 . determinant and metrices4 Marks
MCQ
Find adjoint of each of the matrices : $\left[\begin{array}{ll}1 & 2 \\ 3 & 4\end{array}\right]$
  • A
    $\left[\begin{array}{cc}4 & 2 \\ -3 & 1\end{array}\right]$
  • B
    $\left[\begin{array}{cc}-4 & -2 \\ -3 & 1\end{array}\right]$
  • ✓
    $\left[\begin{array}{cc}4 & -2 \\ -3 & 1\end{array}\right]$
  • D
    $\left[\begin{array}{cc}4 & -2 \\ 3 & 1\end{array}\right]$
✓

Answer

Correct option: C.
$\left[\begin{array}{cc}4 & -2 \\ -3 & 1\end{array}\right]$
c
Let $A=\left[\begin{array}{ll}1 & 2 \\ 3 & 4\end{array}\right]$

We have,

$A_{11}=4, A_{12}=-3, A_{13}=-2, A_{22}=1$

$\therefore a d j A=\left[\begin{array}{ll}A_{11} & A_{21} \\ A_{12} &  A_{22}\end{array}\right]=\left[\begin{array}{cc}4 & -2 \\ -3 & 1\end{array}\right]$

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