CAPE Pure Mathematics Unit 2 · May/June 2016 · Paper 1 · Question Q32

A is a 3 \times 3 matrix with determinant 14. If the matrix of cofactors of A is \begin{pmatrix} 4 & -14 & -2 \\ 3 & -7 & -5 \\ 1 & 7 & 3 \end{pmatrix}, then A^{-1} =

1. (A)\frac{1}{14} \begin{pmatrix} 4 & -14 & -2 \\ 3 & -7 & -5 \\ 1 & 7 & 3 \end{pmatrix}
2. (B)\frac{1}{14} \begin{pmatrix} 4 & 3 & 1 \\ -14 & -7 & 7 \\ -2 & -5 & 3 \end{pmatrix}
3. (C)-\frac{1}{14} \begin{pmatrix} 4 & -14 & -2 \\ 3 & -7 & -5 \\ 1 & 7 & 3 \end{pmatrix}
4. (D)-\frac{1}{14} \begin{pmatrix} 4 & 3 & 1 \\ -14 & -7 & 7 \\ -2 & -5 & 3 \end{pmatrix}