# How do you find the domain of |2x + 1|?

The domain is all real numbers, or $\mathbb{R}$.
The domain of a real function, or expression, is a set that contains every possible value the independent variable ($x$, in our case) can take, so that the evaluation is possible and makes sense.
$\left\mid 2 x - 1 \right\mid$ makes sense for any real value of $x$, therefore its domain is all real numbers.