start adding 9 on both sides
[tex]\begin{gathered} x^2-9+9=16+9 \\ x^2=25 \end{gathered}[/tex]take the square root on both sides
[tex]\begin{gathered} \sqrt[]{x^2}=\sqrt[]{25} \\ x=\pm5 \end{gathered}[/tex]the solutions of the equation are x=5 and x=-5.
