Answer: x = 0
Work Shown:
y = -3x^2 - 12 is the same as y = -3x^2 + 0x + (-12)
Compare this to y = ax^2 + bx + c, and we'll find that
a = -3
b = 0
c = -12
Plug the 'a' and 'b' values into the formula below and simplify
h = -b/(2a)
h = -0/(2*(-3))
h = 0
The x coordinate of the vertex is x = 0, so the axis of symmetry is also x = 0.
The axis of symmetry lays perfectly on top of the y axis.