The graph of the equation $y =ax^2 + bx + c$ where a, b, and c are constants, is a parabola with axis of symmetry x = -3. Find b/a.
A quick lookup finds this:
For a quadratic function in standard form, y=ax2+bx+c , the axis of symmetry is a vertical line x=−b/2a .
-b/2a = -3
b/a = 6