What is the axis of symmetry for f(x) = -3x^2+12x-6

-3x^2 + 12x -6
a = -3
b = 12
We calculate the vertex "x" value with this formula:
(vertex "x value")  = -b / (2*a)
(vertex "x value")  = -12 / -6
The vertex "x" value equals the axis of symmetry value.
The axis of symmetry is at x = 2.

Source:
http://www.1728.org/quadr3.htm

Idon’t exactly understand but i think dbc=rst