Concept:
A parabola of the form
\[
x^2 + Dx + Ey + F = 0
\]
represents a vertical parabola (since only \(x^2\) is present).
To find its axis:
• Convert the equation into vertex form by completing the square.
• The axis of symmetry is a vertical line passing through the vertex: \( x = \text{constant} \).
Step 1: Group the \(x\)-terms and complete the square.
\[
x^2 + 6x + 4y + 5 = 0
\]
\[
(x^2 + 6x) + 4y + 5 = 0
\]
Complete the square:
\[
x^2 + 6x = (x+3)^2 - 9
\]
Substitute:
\[
(x+3)^2 - 9 + 4y + 5 = 0
\]
\[
(x+3)^2 + 4y - 4 = 0
\]
Step 2: Rewrite in standard form.
\[
(x+3)^2 = -4(y - 1)
\]
Step 3: Identify the axis of symmetry.
The vertex form is:
\[
(x - h)^2 = 4a(y - k)
\]
where the axis is:
\[
x = h
\]
Here, \( h = -3 \), so the axis is:
\[
x = -3
\]
\[
\Rightarrow x + 3 = 0
\]