You have to understand the problem clearly before trying to answer the question. Only thing that needs to be done to answer the question is adding 5 with f(x). This will yield the required result.
g(x) = f(x) + 5
= (4x^2 - 8) + 5
= 4x^2 - 8 + 5
= 4x^2 - 3
I hope that this is the answer that you were looking for and the answer has actually come to your desired help.
