Answer
$$ (-2,-12)$$
Work Step by Step
Completing the square in order to write the equation in the form $a(x-h)^2+k$, we find:
$$3\left(x^2+4x+2^2-2^2\right) \\ 3\left(x+2\right)^2-12$$
The vertex is $(h,k)$, so we see that the vertex is:
$$ (-2,-12)$$
