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Exercise 2.2 · Q22

Q.Find the inverse of the following matrix. [2−3−12]\begin{bmatrix} 2 & -3 \\ -1 & 2 \end{bmatrix}

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Step 1: A=[2−3−12]A=\begin{bmatrix} 2 & -3 \\ -1 & 2 \end{bmatrix}, ∣A∣=2(2)−(−1)(−3)=4−3=1≠0|A|=2(2)-(-1)(-3)=4-3=1\neq0.

Step 2: [2−3−12]A−1=[1001]\begin{bmatrix}2&-3\\-1&2\end{bmatrix}A^{-1}=\begin{bmatrix}1&0\\0&1\end{bmatrix}. Use R1↔R2R_1\leftrightarrow R_2: [−122−3]A−1=[0110]\begin{bmatrix}-1&2\\2&-3\end{bmatrix}A^{-1}=\begin{bmatrix}0&1\\1&0\end{bmatrix}.

Step 3: R1→−R1R_1\to-R_1: [1−22−3]A−1=[0−110]\begin{bmatrix}1&-2\\2&-3\end{bmatrix}A^{-1}=\begin{bmatrix}0&-1\\1&0\end{bmatrix}. …

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