Chapter 2 - Linear and Quadratic Functions - Section 2.8 Equations and Inequalities Involving the Absolute Value Function - 2.8 Assess Your Understanding - Page 182: 40

$(-9,9)$. Refer to the graph below.

Using the definition of the absolute value, we have $$ |x|\lt 9\Longrightarrow -9\lt x\lt 9 $$ and this can be written in terms of intervals as all $x$ in the interval $(-9,9)$. To graph the solution set, plot holes (or hollow dots) at $-9$ and $9$ then shade the region in between them. (Refer to the graph below)