persamaan grafik fungsu kuadrat diatas berapa ya

[tex]2 = \frac{ - b}{2a} \\ b = - 4a[/tex]
[tex]6 = - \frac{ {b}^{2} - 4ac}{4a} \\ 6 = \frac{ {b}^{2} + bc }{b} \\ 6b - {b}^{2} = bc \\ c = 6 - b \\ b = 6 - c[/tex]
grafik (-x²) karena menghadap bawah
b = -4(-1)
b = 4
c = 6-4
c = 2
f(x) = -x²+4x+2