Question

If \( A = \begin{bmatrix} 4 & 5 2 & 1 \end{bmatrix} \), find \( A^{-1} \).

• A. \( \begin{bmatrix} 1/6 & -5/6 -1/3 & 2/3 \end{bmatrix} \)
• B. \( \begin{bmatrix} -1/6 & 5/6 1/3 & -2/3 \end{bmatrix} \)
• C. \( \begin{bmatrix} -1 & 5 2 & -4 \end{bmatrix} \)
• D. \( \begin{bmatrix} 4 & -5 -2 & 1 \end{bmatrix} \)

Hint:

For \(2 \times 2\) matrices, always use the shortcut: Swap diagonal elements, change signs of off-diagonal elements, then divide by determinant.

Answer 1

The Correct Option is B