Which operation involving complex numbers requires the use of a conjugate to be carried out?

Step-by-step explanation:

Rationalization.  

                                                                              2 + i

For example:  " rationalize the denominator of  "

                                                                               -3 + i

i think is 3 and 6. this took me 10 min to think.hope to and hope that my answer is brainliest.(follow me )