Answer:
In the given parabola
the line of symmetry is the axis x = -3
Step-by-step explanation:
Here, the given equation of the parabola is : 
Now, in the <u>Standard Form of the Parabolic Equation</u>:
,
The axis of symmetry is a vertical line x = −b / 2 a .
Now, here comparing the given parabolic equation with teh standard form, we get :
a = 1 , b = 6 and c = -9
So, the axis of symmetry = 
Hence, here in the given parabola
the line of symmetry is the axis x = -3.