CUET · MATHS · PYQ PAPER 2023
If \(A=\left[\begin{array}{ll}3 & -5 \\ 4 & -7\end{array}\right]\), then \(A^{-1}\) is:
- A \(\left[\begin{array}{ll}-7 & 5 \\ -4 & 3\end{array}\right]\)
- B \(\left[\begin{array}{cc}7 & 5 \\ 4 & -3\end{array}\right]\)
- C \(\left[\begin{array}{cc}-7 & -5 \\ -4 & 3\end{array}\right]\)
- D \(\left[\begin{array}{ll}7 & -5 \\ 4 & -3\end{array}\right]\)
Answer & Solution
Correct Answer
(D) \(\left[\begin{array}{ll}7 & -5 \\ 4 & -3\end{array}\right]\)
Step-by-step Solution
Detailed explanation
\(\det(A) = (3)(-7) - (-5)(4) = -21 + 20 = -1\) \(A^{-1} = \frac{1}{-1}\left[\begin{array}{cc}-7 & -(-5) \\ -4 & 3\end{array}\right] = -1\left[\begin{array}{cc}-7 & 5 \\ -4 & 3\end{array}\right] = \left[\begin{array}{cc}7 & -5 \\ 4 & -3\end{array}\right]\)
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