Question

what is complex conjugate?​

Answer 1

parts identical and their imaginary parts of equal magnitude but opposite sign.

"replace each element of the matrix by its complex conjugate"

Answer 2

the complex conjugate of a complex number is the number with an equal real part and an imaginary part equal in magnitude but opposite in sign. For example, the complex conjugate of 3 + 4i is 3 − 4i.