$a)$  

$f\left(x\right)=\{\begin{array}{ll}2& x\in \left(-\infty ;-3\right)\\ x-3& x\in \left(-3;1\right)\cup \left\{3\right\}\\ -3& x\in \left(1;+\infty \right)\cup \left\{1\right\}\end{array}$ $f\left(x\right)=\{\begin{array}{ll}2& x\in \left(-\infty ;-3\right)\\ x-3& x\in \left(-3;1\right)\cup \left\{3\right\}\\ -3& x\in \left(1;+\infty \right)\cup \left\{1\right\}\end{array}$         

$b)$  

$f\left(x\right)=\{\left(x+1x=3\right)$