Write the term with the factor a 1 1a23 in the fourth-order determinant (to analyze the process, thank you! )

There are two terms in the fourth-order determinant that contain factors a12a24: a12a24a34a41and -A 12A24A 3 143. The fourth-order determinant has P3=6 terms of the specified element; The project with two specified elements has P2=2 projects; An item with three (and four) elements is p1= P0 =1; N (2431) =1+2+1= 4, n (2413) =1+2+0 = 3, so a12a24a. A 12a24a3 1a43 was negative.