Answer
$f(x)=-2(x-3)^{2}+18$
Graph: See image below
Work Step by Step
The standard form of a parabola is in the form of $f(x)=a(x−h)^{2}+k. $
"a" will be the coefficient of $x^{2}$ which in this case is -2
"h" will be the x-term divided by 2 and "a". Therefore h=12/2/-2=-3.
Finally ''k" will be the constant term $−ah^{2}$. Using this k is found to be 18.
Therefore the answer is $f(x)=-2(x-3)^{2}+18$
