hello everyone! im new to this forum, found it by google because i couldnt find an answer anywhere else, i am trying to study for a college placement test and i am having some trouble trying to remember math i learned 3 years ago, here is the link to the math sample questions:

Code:

http://www.nvcc.edu/woodbridge/TCenter/mathsample.htm

i am stuck on number 39, second part. If g is a function such that g(x) = ax^2 –3 and g(3) = 3, find g(6). (answer: 21)

i need to know the process of how to do it, many thanks everyone!!