(1) Write the first and second elements of the third row after a33 respectively in the third
row of the determinant, likewise write last and third elements of the same row before a31
respectively in the third row of determinant. Now write the first element of the second row
after last element a23 in the second row of the determinant and the last element before
the first element a21 in the second row of the determinant. Thus we obtain following
scheme 6.