1. If the solution set of the inequality $|x+a|<b$ with respect to $x$ is $\{x \mid 2<x<4\}$, then the value of $a b$ is $\qquad$
$$
|x+a|<b \Rightarrow -a-b<x<-a+b \Rightarrow a=-3, b=1 \Rightarrow ab=-3 .
$$