# How do you find the domain of the function f(x)= -x^2 + 2x +3?

This is a quadratic function i.e. $a {x}^{2} + b x = c$, all quadratic functions have range:
$\left\{x | x \in \mathbb{R}\right\}$ or Interval notation $\left(- \infty , \infty\right)$