Answer
$f(x)=-(x+5)^{2}+26$
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 -1
"h" will be the x-term divided by 2 and "a". Therefore h=10/2/-1=-5.
Finally ''k" will be the constant term $−ah^{2}$. Using this k is found to be 26.
Therefore the answer is $f(x)=-(x+5)^{2}+26$
