The x-coordinate of the vertex of a parabola y = ax^2 + bx + c is x = -b / (2a).
Here, a = -3 and b = -10, so the x-coord of the vertex is x = 10 / (2*-3), or
x = 10 / (-6) = -5/3
and so the y-coordinate is y = -3(-5/3)^2 - 10(-5/3) = 25/3
The vertex of this parabola is (-5/3, 25/3). (answer)
