persamaan kuadrat yang melalui titik (0,3) (2,3) dan (1,1)

y = ax^2 + bx + c
3 = c                      substitusi x = 0
3 = (2^2) a + 2b + c
1 = (1^2) a + b + c

3 = 4a + 2b + 3
1 = a + b + 3

4a + 2b = 0
a + b = -2                            a = -2 - b
4( -2 - b ) = -2b
-8 - 4b = -2b
-8 = 2b
b = -4

a = -2 - (-4)
a = 2

y = 2x^2 - 4x +3