Answer :
[tex]|2n+5|\geq9\\
2n+5\geq 9 \vee 2n+5\leq-9\\
2n\geq4 \vee 2n\leq-14\\
n\geq2 \vee n\leq-7\\
n\in(-\infty,-7\rangle\cup\langle2,\infty)[/tex]
[tex]|2n+5|\geq9\iff2n+5\geq9\ or\ 2n+5\leq-9\ \ \ |subtract\ 5\ from\ both\ sides\\\\2n\geq4\ or\ 2n\leq-14\ \ \ \ \ |divide\ both\ sides\ by\ 2\\\\\boxed{n\geq2\ or\ n\leq-7}\\\\Answer:\boxed{\boxed{n\in(-\infty;-7]\ \cup\ [2;\ \infty)}}[/tex]
