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Question: Answered & Verified by Expert
The inverse of the matrix \( A=\left[\begin{array}{lll}2 & 0 & 0 \\ 0 & 3 & 0 \\ 0 & 0 & 4\end{array}\right] \) is
MathematicsSets and RelationsKCETKCET 2014
Options:
  • A \( \left[\begin{array}{lll}2 & 0 & 0 \\ 0 & 3 & 0 \\ 0 & 0 & 4\end{array}\right] \)
  • B \( \frac{1}{24}\left[\begin{array}{lll}1 / a & 0 & 0 \\ 0 & 1 / b & 0 \\ 0 & 0 & 1 / c\end{array}\right] \)
  • C \( \frac{1}{24}\left[\begin{array}{lll}2 & 0 & 0 \\ 0 & 3 & 0 \\ 0 & 0 & 4\end{array}\right] \)
  • D \( \frac{1}{24}\left[\begin{array}{llll}1 & 0 & 0 \\ 0 & 1 & 0 \\ 0 & 0 & 1\end{array}\right] \)
Solution:
2234 Upvotes Verified Answer
The correct answer is: \( \frac{1}{24}\left[\begin{array}{lll}1 / a & 0 & 0 \\ 0 & 1 / b & 0 \\ 0 & 0 & 1 / c\end{array}\right] \)
Given that \( A=\left[\begin{array}{lll}2 & 0 & 0 \\ 0 & 3 & 0 \\ 0 & 0 & 4\end{array}\right] \)
Now \( A^{-1}=\left[\begin{array}{ccc}1 / 2 & 0 & 0 \\ 0 & 1 / 3 & 0 \\ 0 & 0 & 1 / 4\end{array}\right] \)
If \( A=\left[\begin{array}{ccc}a & 0 & 0 \\ 0 & b & 0 \\ 0 & 0 & c\end{array}\right] \), then \( A^{-1}=\left[\begin{array}{ccc}1 / a & 0 & 0 \\ 0 & 1 / b & 0 \\ 0 & 0 & 1 / c\end{array}\right] \)
When \( a \neq 0, b \neq 0, c \neq 0 \)

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