Substitute (0, 12) into the model: .

So .... (A)

Substitute (-2, 0) and (6, 0) into (A):

.... (1)

.... (2).

Solve equations (1) and (2) simultaneously for a and b (things might be simpler if you simplify them first).

By the way,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.Analysis

You're not to know this of course and I'm not having a dig atyou.... 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 ....