Answer
domain$:\quad \mathbb{R}=(-\infty,\infty)$
range$:\quad [18,\infty)$
Work Step by Step
$f(x)= ax^{2}+b\mathrm{x}+c \quad $or $\quad f(x)=a(x-h)^{2}+k$
A quadratic function is defined for all real numbers,
domain$:\quad \mathbb{R}=(-\infty,\infty)$
The graph of f(x) is a parabola.
If the parabola opens down, the vertex is its maximum point.
If the parabola opens up, the vertex is its minimum point.
At $x=-6$ the minimum of $f(x)$ is $18$ (parabola opens up).
(for all the other x, function values are more than $18)$
The range of f is $[18,\infty)$
