Answer
See below
Work Step by Step
The vertex form of a quadratic function: $y=a(x-h)^2+k$
The vertex is $(-4,-6)$, so we know $h=-4\\k=-6$
The function becomes: $y=a(x-(-4))^2+(-6)\\y=a(x+4)^2-6$
We notice that $(2,3)$ is on the graph, so we will substitute:
$3=a(2+4)^2-6\\\rightarrow 36a-6=3\\ \rightarrow 36a=9\\\rightarrow a=\frac{1}{4}$
Hence, $y=\frac{1}{4}(x+4)^2-6$