Answer:
y = -3
Explanation:
x = ⅛ (y + 3)² − 1
This is a horizontal parabola, so the axis of symmetry is a horizontal line, y = k.
The vertex of the parabola is (-1, -3). The axis of symmetry passes through the vertex. Therefore, the equation is y = -3.
Graph: desmos.com/calculator/seu44kskhw