Answer
$f(x)=(x+3)^2-7$
Work Step by Step
The standard form of a parabola is in the form $f (x) = a(x - h)^2 + k$.
a will be the coefficient of $x^2$. In this case it is 1.
h will be the x term divided by 2 and a. $6/2/1=3$
And finally k will be the constant term $-ah^2$.
Using these steps we find k to be -7.
Therefore the answer is $f(x)=(x+3)^2-7$.