1.
對稱軸是直線x=2,與x軸的另一交點為(3,0)
y = a(x - 1)(x - 3)
過點B:-3 = a(0 - 1)(0 - 3),a = -1
y = -(x - 1)(x - 3) = -x² + 4x - 3
2.
頂點是(-2,3),拋物線:y = a(x + 2)² + 3
過點(-1,5):5 = a(-1+2)² + 3,a = 2
y = 2x² + 8x + 11
3.
與x軸的交點(-2,0),(4,0):y = a(x + 2)(x - 4)
過點(1,-9/2):-9/2 = a(1 + 2)(1 - 4),a = 1/2
y = x²/2 - x - 4
4.
對稱軸是直線x=1,與x軸的交點:(-3,0),(5,0)
y = a(x + 3)(x - 5)
過點(1,16):16 = a(1 + 3)(1 - 5),a = -1
y = -x² + 2x + 15