## College Algebra (6th Edition)

domain$:\quad \mathbb{R}=(-\infty,\infty)$ range$:\quad [18,\infty)$
$f(x)= ax^{2}+b\mathrm{x}+c \quad$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 $[18,\infty)$