MHT CET · Maths · Matrices
If matrix \(\mathrm{A}=\left[\begin{array}{ll}1 & 2 \\ 4 & 3\end{array}\right]\) is such that \(\mathrm{AX}=\mathrm{I}\), where \(\mathrm{I}\) is \(2 \times 2\) unit matrix, then \(X=\)
- A \(\frac{1}{5}\left[\begin{array}{ll}-3 & -2 \\ -4 & -1\end{array}\right]\)
- B \(\frac{1}{5}\left[\begin{array}{cc}-3 & 2 \\ 4 & -1\end{array}\right]\)
- C \(\frac{1}{5}\left[\begin{array}{ll}3 & 2 \\ 4 & 1\end{array}\right]\)
- D \(\frac{1}{5}\left[\begin{array}{cc}3 & -2 \\ -4 & 1\end{array}\right]\)
Answer & Solution
Correct Answer
(B) \(\frac{1}{5}\left[\begin{array}{cc}-3 & 2 \\ 4 & -1\end{array}\right]\)
Step-by-step Solution
Detailed explanation
\(\mathrm{AX}=\mathrm{I} \Rightarrow \mathrm{X}=\mathrm{A}^{-1}=\mathrm{A}^{-1}\)
\(\Rightarrow X=\left[\begin{array}{ll}1 & 2 \\ 4 & 3\end{array}\right]^{-1}=\frac{-1}{5}\left[\begin{array}{cc}3 & -2 \\ -4 & 1\end{array}\right]=\frac{1}{5}\left[\begin{array}{cc}-3 & 2 \\ 4 & -1\end{array}\right]\)
\(\Rightarrow X=\left[\begin{array}{ll}1 & 2 \\ 4 & 3\end{array}\right]^{-1}=\frac{-1}{5}\left[\begin{array}{cc}3 & -2 \\ -4 & 1\end{array}\right]=\frac{1}{5}\left[\begin{array}{cc}-3 & 2 \\ 4 & -1\end{array}\right]\)
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