Question

How do I do this? , it’s making me confused

Answer 1

you remember vertex: h,k in (x-h)²+k..

replace in that. In that graph vertex: (10, -20)

So in that Equation, a(x-10)²-20, a<0 since it is maximum graph.

I cannot find the full Equation but from what I can see you can find h,k and the fact that a<0