Find the vertex and axis of symmetry of the parabola when y=-3x^2+12-8

Answer 1

Don't you mean
y = 3x^2 +12x -8 ?

If so, "complete the square" and rewrite it as
y = 3(x^2 + 4x + 4)- 20
= 3(x+2)^2 -20

That is symmetric about x = -2, and has a vertex at
x = -2, y = -20

Answer 2

how to graph