## Thomas' Calculus 13th Edition

$x \lt -2$
Multiply the inequality with $-\displaystyle \frac{1}{2}\quad$ (to isolate x). Apply rule 4 from the table "Rules for Inequalities", by which multiplying with a negative number, the inequality changes direction $x \lt -2$ This inequality describes an open interval, $x\in(-\infty,-2)$ See table "Types of intervals."