belom ada yang jawab, mohon bantuannya sih :)

f(x) = -x^2 + px + q => a = -1
Puncak = (2,9) = (xp, yp)
f(x) = a(x - xp)^2 + yp
f(x) = -1(x - 2)^2 + 9
f(x) = -1(x^2 - 4x + 4) + 9
f(x) = -x^2 + 4x - 4 + 9
f(x) = -x^2 + 4x + 5
Jadi p = 4 dan q = 5