According to the diagonal relationship, each element can only have two lines in each product, so one element can only appear in two products. If * * * is drawn three times, six projects can contain this element.

In the determinant of order n, when one element takes precedence as an element in the expansion item, the rest elements can only be selected from the remaining sub-formula of order n- 1, and the method is (n- 1)! Kindness For the fourth-order determinant, there is (4- 1)! =6 kinds, so there are 24 items after expansion according to the above method.

Extended data:

Precautions:

The calculation of the fourth-order determinant must first be reduced. For determinant a of order n, it can be reduced according to the expansion of a certain row or column, usually the first row or column. Because this symbol is easy to determine. This is the general idea.

If there are more zeros in the upper right corner of the determinant or the rows and columns can be converted into the block form mentioned in Lesson 7 by exchanging two rows (or two columns) of the determinant, then the calculation of the determinant is the block method, that is, using the properties of Krj+ri and Kcj+ci, the determinant is calculated by exchanging two rows and two columns.

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