Question

the x coordinate of the vertex f(x)=ax^2 + bx + c

Answer 1

Will we be completing the square or just writing down the answer?

Answer 2

Okay, now answer my question. Completing the Square or knowing that result, just write down the answer?

Answer 3

just the answer

Answer 4

Both methods lead to just the answer. You still haven't picked. Either you know it or you don't.

If you do not know the fast way, which it appears you don't, you should proceed with Completing the Square. Go!!