Answer
$(-\infty,a]\cup[b,c]\cup[d,\infty)$
Work Step by Step
1. The cut points can be identified as $a,b,c,d$,
2. Build a table as shown in the figure and identify the signs in each region.
3. Based on the end results from the table, the solutions for the inequality can be
found as $(-\infty,a]\cup[b,c]\cup[d,\infty)$