Calculation of goodwill query

hi im a new student to P2 and i noticed in the video lectures that the “old” method that was used for the calculation of goodwill is not used as mike said that he’s not allowed to teach that anymore. i was wondering is it that that method is just not taught or would one be penalised for using it in an exam. i would really like to know as i am comfortable with that method and i would like to know if i would have to learn a new one or not.

Thanks