Answer
$(-\infty,0]$ and $[0,\infty)$
Work Step by Step
The function decreases in an interval when, moving from left to right, the y-values continue to get smaller for x-values in that interval. For the graph in the question, there are two intervals for which the y-values decrease.
First, the y-values decrease for all values of $x$ between $-\infty$ and $0$. Since $0$ is included in the interval, a square bracket will be used on its side while on the other end, the symbol $-\infty$ is always supported by a parenthesis.
Secondly, the y-values decrease for all values of $x$ between $0$ and $\infty$. Since $0$ is included in the interval, a square bracket will be used on its side while on the other end, the symbol $\infty$ is always supported by a parenthesis.
Therefore, the function decreases in the intervals $(-\infty,0]$ and $[0,\infty)$.
