Answer:
a = b = 1 , c = - 8
Step-by-step explanation:
ax² + bx + c = y
( - 5 )² a - 5b + c = 12
c = - 8
3² a + 3b + c = 4
25a - 5b - 8 = 12 ⇔ 25a - 5b = 20 ⇔ 5a - b = 4 ........ (1)
9a + 3b - 8 = 4 ⇔ 9a + 3b = 12 ⇔ 3a + b = 4 .......... (2)
(1) + (2)
8a = 8 ; a = 1
b = 1
y = x² + x - 8
