Take the b term, in this case 6, divide it by 2 (now you have 3), and then square that quotient (9). Now add that result to both sides:
x² + 6x + 9 = 18 + 9
(x + 3)² = 27
Square root both sides so you are left with only (x + 3) on the left side.
√(x + 3)² = √27
x + 3 = +/- √27
Simplify the √27:
x + 3 = +/- 3√3
Subtract 3 from both sides to isolate variable x:
x = - 3 +/- 3√3
Your answers are:
x = - 3 - 3√3 and x = - 3+ 3√3
