So .... (A)
Substitute (-2, 0) and (6, 0) into (A):
Solve equations (1) and (2) simultaneously for a and b (things might be simpler if you simplify them first).
By the way, Analysis has a very different mathematical meaning to the very narrow (and in my opinion, stupid) one that is used in many Australian secondary school classrooms and curriculum documents.
You're not to know this of course and I'm not having a dig at you .... in future it would be better to refer to the sort of question from which this bit is taken from as an extended response question ....