1 Introduction
In the matrix theory and linear algebra, determinant of a square matrix very important. By [4], the basic formula to
compute the determinant of a square matrix of order n, such as � = ���
, is equal to
� � = ��� � = � = ��� �
1 … �
�
�1…�� ∈��
�1�1 … ����
Where ��� �
1 … �
�
=
+1
−1
, �� �
1 … �
�
�� �� ���� �����������
, �� �
1 … �
�
�� �� ��� �����������
.
Also Dodgson in 1866 [1] and Salihu in 2012 [3], offered two methods for compute the determinant of square
matrix of order n that we using of their methods for proof of the new method in this article. whereas for compute the
determinant of a square matrix, always we used of simple methods, therefore in this article we present a simple
method for compute the square matrix of order 4. For this work we offer a new definition of fraction that we named
it the duplex fraction. In the next section you can see this definition. Afterward using the duplex fraction and
Dodgson’s condensation method and Salihu’s method we obtain a new method for compute the square matrix of
order 4.