Answer
$(-\infty,\infty)$
Work Step by Step
We are given that $f(x)=2x+3$ and want to determine all possible real numbers $x$ for which $f(x)$ is defined. We can always multiply any real number by 2 and add 3 to the result, so the domain of $f$ is all real numbers, which can be written as $(-\infty, \infty)$.
