Inverse (or its determinant) of an expression in matrices: compute the expression first

1. A.
   $\left(-\dfrac{1}{4}\right)\begin{pmatrix}-3 & 1\\7 & -1\end{pmatrix}$
2. B.
   $\left(\dfrac{1}{4}\right)\begin{pmatrix}-3 & 1\\7 & -1\end{pmatrix}$
3. C.
   $\left(\dfrac{1}{4}\right)\begin{pmatrix}3 & 1\\7 & 1\end{pmatrix}$
4. D.
   $\left(\dfrac{1}{-4}\right)\begin{pmatrix}3 & -1\\7 & 1\end{pmatrix}$

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1. A.
   $\dfrac{1}{95}\begin{bmatrix} 7 & 3 \\ 3 & 4 \end{bmatrix}$
2. B.
   $\dfrac{1}{95}\begin{bmatrix} -7 & 3 \\ 3 & -4 \end{bmatrix}$
3. C.
   $\dfrac{1}{95}\begin{bmatrix} -7 & -3 \\ 3 & 4 \end{bmatrix}$
4. D.
   $\dfrac{1}{95}\begin{bmatrix} 4 & 3 \\ 3 & 7 \end{bmatrix}$

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1. A.
   $\begin{pmatrix}-\frac{1}{2} & 0\\-\frac{3}{2} & \frac{1}{2}\end{pmatrix}$
2. B.
   $\begin{pmatrix}\frac{1}{2} & 0\\\frac{3}{2} & -\frac{1}{2}\end{pmatrix}$
3. C.
   $\begin{pmatrix}\frac{1}{2} & 0\\-\frac{3}{2} & \frac{1}{2}\end{pmatrix}$
4. D.
   $\begin{pmatrix}\frac{1}{2} & 0\\\frac{3}{2} & \frac{1}{2}\end{pmatrix}$

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1. A.
   $\begin{bmatrix} \dfrac{1}{3} & 0 & 0 \\ 0 & -\dfrac{1}{4} & 0 \\ 0 & 0 & \dfrac{1}{26} \end{bmatrix}$
2. B.
   $\begin{bmatrix} \dfrac{1}{3} & 0 & 0 \\ 0 & \dfrac{1}{4} & 0 \\ 0 & 0 & \dfrac{1}{26} \end{bmatrix}$
3. C.
   $\begin{bmatrix} \dfrac{1}{3} & 0 & 0 \\ 0 & \dfrac{1}{4} & 0 \\ 0 & 0 & -\dfrac{1}{26} \end{bmatrix}$
4. D.
   $\begin{bmatrix} -\dfrac{1}{3} & 0 & 0 \\ 0 & \dfrac{1}{4} & 0 \\ 0 & 0 & -\dfrac{1}{26} \end{bmatrix}$

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1. A.
   $\dfrac{1}{5}$
2. B.
   $25$
3. C.
   $\dfrac{1}{25}$
4. D.
   $-25$

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1. A.
   $\begin{pmatrix} 1 & -2 \\ 1 & -3 \end{pmatrix}$
2. B.
   $\begin{pmatrix} 3 & -2 \\ 1 & -1 \end{pmatrix}$
3. C.
   $\begin{pmatrix} -3 & 2 \\ -1 & 1 \end{pmatrix}$
4. D.
   $\begin{pmatrix} -3 & 2 \\ -1 & -1 \end{pmatrix}$

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