Step-by-step explanation:
[tex]f(x) = - 5x + 3 \\ g(x) = - {x}^{2} \\ (f + g)(x) \\ = f(x) + g(x) \\ = - 5x + 3 - {x}^{2} \\ (f + g)(x) = - {x}^{2} - 5x + 3 \\ [/tex]