Respuesta :

arewar
(f+g)(x) is simply saying add these two problems together.

(2x+6) + (4x^2) 

Parenthesis are now useless, as there is only addition.

2x + 6 + 4x^2

Reorder, cause it's pretty and familiar

4x^2 + 2x + 6

We could further simplify

2(2x^2 + x + 3)