I know (and you should know it) that this function has a form 

f(x) = a*(x-(-9)*(x-(-3)) = a*(x+9)*(x+3),

where "a" is a real constant.

To determine this constant, I will calculate the function f(x) at the point x = -6, where the vertex is. It is

f(-6) = a*(-6 +9)*(-6+3) = a*3*(-3) = -9a.

Thus, I must find the value of "a" from this equation: 

f(-6) = -1,  which becomes  -9a = -1.

Hence,  a =  = .

Answer.  The function under the question is f(x) = .

You may open parentheses if you need.