SOLUTION
From the question
[tex]\begin{gathered} f(x)=3+5x \\ g(x)=2x^2-4 \\ we\text{ want to find } \\ (f+g)(x) \end{gathered}[/tex]This becomes
[tex]\begin{gathered} (f+g)(x)=f(x)+g(x) \\ =3+5x+2x^2-4 \\ collecting\text{ like terms we have } \\ =3-4+5x+2x^2 \\ =-1+5x+2x^2 \\ rearranging\text{ we have } \\ 2x^2+5x-1 \end{gathered}[/tex]Hence the answer is
[tex]2x^2+5x-1[/tex]