## Precalculus (10th Edition)

a) $x|(-\infty,-1]\cup(-1,1)\cup(3,\infty)$. b) $[1,2) \cup (2,3]$.
As we can see on the graph: a) $f(x)>0$ in the intervals $(-\infty,-1]\cup(-1,1)\cup(3,\infty)$ because the graph of the function is above the x-axis (which is $y=f(x)=0$) on these intervals. $-1$, $1$ and $3$ are not included because the inequality involves greater than. b) $f(x)\leq0$ in the intervals $[1,2) \cup (2,3]$ because the graph of the function is below or on the x-axis (which is $y=f(x)=0$) on these intervals. $1$ and $3$ are included because the inequality involves less than or equal to.