Question 52871
Using the square root property:
{{{(x+3)^2=81}}}
{{{sqrt((x+3)^2)=+-sqrt(81)}}}
x+3=+or-9
x+3-3=-3+or-9
x=-3-9
x=-12
and
x=-3+9
x=6
x=-12;x=6
Not all teachers require set notation: 
In set notation x={-12,6}