Question on: JAMB Mathematics - 2011

The inverse of matrix N = (\begin{vmatrix} 2 & 3 \

1 & 4\end{vmatrix}) is

A
\(\frac{1}{5}\) \(\begin{vmatrix} 2 & 1 \ 3 & 4\end{vmatrix}\)
B
\(\frac{1}{5}\) \(\begin{vmatrix} 4 & -3 \ -1 & 2\end{vmatrix}\)
C
\(\frac{1}{5}\) \(\begin{vmatrix} 2 & -1 \ -3 & 4\end{vmatrix}\)
D
\(\frac{1}{5}\) \(\begin{vmatrix} 4 & 3 \ 1 & 2\end{vmatrix}\)
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Correct Option: B

N = [2 3]

N-1 = (\frac{adj N}{|N|})

adj N = (\begin{vmatrix} 4 & -3 \ -1 & 2 \end{vmatrix})

|N| = (2 x4) - (1 x 3)

= 8 - 3

=5

N-1 = (\frac {1}{5}) (\begin{vmatrix} 4 & -3 \ -1 & 2 \end{vmatrix})

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