Answer
$(-1,9)$
Work Step by Step
Since the equation is not in standard form, use the formula $x=\frac{-b}{2a}$ to find the $x$ coordinate of the vertex.
$f(x)=-x^{2}-2x+8$
$x=\frac{-(-2)}{2(-1)}=-1$
Now plug in the $x$ value in the original equation.
$-(-1^{2})-2(-1)+8=9$
$(-1,9)$
