If the quadratic equation x² + 6x + 9 = 0 is represented graphically, what is the vertex of the parabola?
Answer: C. (-3, 3)
The vertex of the parabola given by the equation ax² + bx + c is at the point (-b/2a, f(-b/2a)). Here, -b/2a = -6/2 = -3. Plugging x = -3 into the equation gives f(-3) = 9 - 18 + 9 = 0, so the vertex is (-3, 0).