Caranya kayak gimana ya?

jawab
grafik melalui
(0,-2) , (2,-6) dan (8,6)

grafik y = ax² + bx + c
(0,-2) → -2 = c

(2, -6) → -6 = a(2)² + b(2) - 2 → -6 = 4a + 2b - 2
4a + 2b = - 4 | bagi 2
2a + b = - 2 (pers.1)

(8,6) →  6 = a(8²) + b(8) - 2 → 6 = 64a + 8b - 2
64 a + 8b = 8 | bagi 8
8 a + b = 1 (pers 2)

2a + b = - 2
8a + b = 1 || (-)
-6a  = - 3 → a = 1/2
2a +  b = -2 → b = -2a - 2 = -2(1/2) - 2 = - 3

y = ax² + bx + c
y = 1/2  x² - 3 x - 2