Does anyone know how to solve this?

For f(x)=2x+3 and g(x)=x^2- 8 find (f+g) (x)

The domain of a function can be represented by which one of the following options? o a. a set of output values o b. a set of f(x) values o c. a set of input values o d. a set of both input and output values

On #16 : explain how factoring a trinomial, ax^2+ bx+ c, when a does not equal 1 different from factoring a trinomial when a = 1.