What is the cofactor expansion of det(A)\det(A)det(A) for A=(a11a12a21a22)A = \begin{pmatrix} a_{11} & a_{12} \\ a_{21} & a_{22} \end{pmatrix}A=(a11a21a12a22) along the first row?
a11a22−a12a21a_{11}a_{22} - a_{12}a_{21}a11a22−a12a21
a11a22+a12a21a_{11}a_{22} + a_{12}a_{21}a11a22+a12a21
a11a21−a12a22a_{11}a_{21} - a_{12}a_{22}a11a21−a12a22
a11a12−a21a22a_{11}a_{12} - a_{21}a_{22}a11a12−a21a22