[tex](x+7)^2=81\iff x+7=\pm\sqrt{81}\\\\x+7=-9\ \vee\ x+7=9\qquad\text{subtract 7 from both sides}\\\\\boxed{x=-16\ \vee\ x=2}[/tex]
(x + 7)² = 81
x + 7 = √81
x+7 = 9
x = 9 - 7
x = 2
