[tex](f+g)(x)=-4x^{2}[/tex]
1) Let's work on this question of the algebra of functions by adding them up:
[tex]\begin{gathered} f(x)=-5x^2+6 \\ g(x)=x^2-6 \\ -------- \\ (f+g)(x)=-4x^2 \end{gathered}[/tex]
Note that we can only add/subtract like terms.
2) And that is the answer.
