Which of these is the formula for the inverse of a 2×22 \times 22×2 matrix A=(abcd)A = \begin{pmatrix} a & b \\ c & d \end{pmatrix}A=(acbd)?
1ad−bc(d−b−ca)\frac{1}{ad-bc} \begin{pmatrix} d & -b \\ -c & a \end{pmatrix}ad−bc1(d−c−ba)
1ad−bc(a−b−cd)\frac{1}{ad-bc} \begin{pmatrix} a & -b \\ -c & d \end{pmatrix}ad−bc1(a−c−bd)
1ad+bc(d−b−ca)\frac{1}{ad+bc} \begin{pmatrix} d & -b \\ -c & a \end{pmatrix}ad+bc1(d−c−ba)
1ad−bc(−dbc−a)\frac{1}{ad-bc} \begin{pmatrix} -d & b \\ c & -a \end{pmatrix}ad−bc1(−dcb−a)