Question

If Element of a row or column are multiplyed.
with cofactor of any other now or calumn. Then their
sum is zero.​

Answer 1

ANSWER:-

✏️Multiplying a row by the co-factors of any other row will mean that the row itself is duplicated in the determinant being evaluated.

✏️It is then like calculating a determinant with two equal rows. And we know that a determinant with elementary row operations is the same determinant

✏️So a determinant with two identical rows will be a determinant with a row replaced by difference of those rows and thus it will be zero.