## Precalculus: Concepts Through Functions, A Unit Circle Approach to Trigonometry (3rd Edition)

Interval Notation: $(-\infty,0]$ Inequality Form: $x\leq 0$.
Since the bracket notation is closed at $0$ and the direction goes to negative infinity, then the interval is $(-\infty,0]$. In terms of inequality, we have $x\leq 0$.