To solve the quadratic equation \(x^2 + 9x + 18 = 0\), we can use the quadratic formula \(x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}\), where \(a\), \(b\), and \(c\) are the coefficients of the equation \(ax^2 + bx + c = 0\).
Step 1: Identify Coefficients
The given quadratic equation is \(x^2 + 9x + 18 = 0\). Here, the coefficients are:
\(a = 1\)
\(b = 9\)
\(c = 18\)
Step 2: Calculate the Discriminant
The discriminant \(D\) is calculated using the formula:
\[
D = b^2 - 4ac
\]
Substituting the values:
\[
D = 9^2 - 4 \cdot 1 \cdot 18 = 81 - 72 = 9
\]
Step 3: Apply the Quadratic Formula
Using the quadratic formula:
\[
x = \frac{-b \pm \sqrt{D}}{2a}
\]
Substituting the values:
\[
x = \frac{-9 \pm \sqrt{9}}{2 \cdot 1} = \frac{-9 \pm 3}{2}
\]