>>244
誤 (a11a33-a13a31)-(a11a23-a12a21)(a11a32-a12a32)/(a11a22-a12a21)
正 ((a11a33-a13a31)-(a11a23-a13a21)(a11a32-a12a31))/a11(a11a22-a12a21)

(a11a33-a13a31)(a11a22-a12a21)-(a11a23-a13a21)(a11a32-a12a31)
=a11a11a22a33-a11a12a21a33-a11a13a22a31+a12a13a21a31-(a11a11a23a32-a11a12a23a31-a11a13a21a32+a12a13a21a31)
=a11(a11a22a33-a12a21a33-a13a22a31-a11a23a32+a12a23a31+a13a21a32)