How can I find the axis of symmetry of a parabola?

I have a maths prelim tomorrow, and I can't figure out how to find axis of symmetry. I missed the cl when that was taught, and my lecturer hasn't had time to show it to me privately. The example in the practice prelim I'm doing is: Y=(X+5)^2-9 And it asks that I find the axis of symmetry. Can someone please tell me how to do this?