The domains of the functions are:
- For \( g(x) = \frac{1}{x+1} \), the domain is \(\boxed{(-\infty, -1) \cup (-1, \infty)}\).
- For \( f(x) = -3x^2 + 8 \), the domain is \(\boxed{(-\infty, \infty)}\).
- For \( p(t) = -9t + 9 \), the domain is \(\boxed{(-\infty, \infty)}\).