What is the axis of symmetry for f(x)=3^2+9x+15?

I'm getting x=-3/2

Step-by-step explanation:

Hello there,
The area of the deck=
90×25=2250 square meters
The area of the patio area=
50×15=750 square meters
Lastly, the total area=
2250m^2+750m^2=3000 meters square.
Then,
The cost of the concrete is $2.3 per sqaute meters, so we just need to take:
3000×2.3=$6900. As a result, the cost to pour the concrete over the deck and patio area is $6900. Hope it help!