Answer
(a) $(-1,1)\cup(2,\infty)$.
(b) $(-\infty,-1]\cup[1,2]$.
Work Step by Step
(a) Based on the given graph, we can identify the solution for $f(x)\lt0$: $(-1,1)\cup(2,\infty)$.
(b) Based on the given graph, we can identify the solution for $f(x)\ge0$: $(-\infty,-1]\cup[1,2]$.
