tentukan persamaan parabola jika diketahui puncaknya di titik (2,9) dan melalui titik (-2,-7)

P ( 2, 9) dan melalui (-2,-7)
y = a ( x - xp) ² + yp
-7 = a ( - 2 - 2)² + 9
-7 - 9 = a (-4)²
-16 = 16 a
a = - 1
Maka pers parabola:
y = - 1(x-2)²+9
y = - 1 (x²-4x+4)+9
y = - x² + 4x - 4 + 9
y = - x² + 4x +5

Diket :
Xp = 2
Yp = 9
x1 = -2
y1 = -7

Jawab :
Y = a(x-xp)^2+yp
Y = a(x-2)^2+9

y1 = a(x1-2)^2+9
-7 = a(-2-2)^2+9
-7-9 = a(-4)^2
16a = -16
a = -1

y = a(x-2)^2+9
y = -(x-2)^2+9
y = -(x^2-4x+4)+9
y = -x^2+4x-4+9
y = -x^2+4x+5

Maaf jika ada kesalahan :)