Poin banyak, tentukan persamaan fungsi kuadrat yang melalui titik-titik (-1,0), (5,0), dan (2,8)

y = a (x - x1)( x - x2)
y = a (x - -1) (x - 5)
y = a (x + 1)(x - 5). melalui (2,8), maka
8 = a (2+1)(2-5)
8 = a (3).(-3)
8 = -9a
a = -9/8 , maka
y = -9/8(x+1)(x-5)
y = (-9/8)x^2 + (36/8)x +45/8

Persamaan Kuadrat

Melalui (p,0) = (-1,0) dan (q,0) = (5,0) :
y = a(x - p)(x - q)
y = a(x - (-1))(x - 5)
y = a(x + 1)(x - 5)

Melalui (2,8)
y = a(x + 1)(x - 5)
8 = a(2 + 1)(2 - 5)
8 = a . 3 . (-3)
8 = -9a
a = -8/9

Persamaan Kuadrat nya :
y = a(x - p)(x - q)
y = -8/9 (x + 1)(x - 5)
y = -8/9 (x² - 4x - 5)
y = -8/9 x² + 32/9 x + 40/9