persamaan kuadrat? (6,0) (2,0) (0,5)

f (x) = ax² + bx + c

maka,

f (6) = 0
a(6)² + b(6) + c = 0
36a + 6b + c = 0
c = -36a - 6b

f (2) = 0
a(2)² + b(2) + c = 0
4a + 2b + c = 0
4a + 2b - 36a - 6b = 0
-32a - 4b = 0
-4b = 32a
4b = -32a
b = -32/4 a
b = -8a

f (1) = 5
a(1)² + b(1) + c = 5
a + b + c = 5
a - 8a - 36a - 6b = 5
-43a - 6(-8a) = 5
-43a + 48a = 5
5a = 5
a = 5/5
a = 1

b = -8a
b = -8(1)
b = -8

c = -36a - 6b
c = -36(1) - 6(-8)
c = -36 + 48
c = 12

f (x) = ax² + bx + c
f (x) = x² - 8x + 12
y = x² - 8x + 12