Answer:
y = -3x² + 20
Step-by-step explanation:
y=ax² + bx + c
pass (-1,17): 17 = a*(-1)² + b*(-1) +c = a-b+c ...(1)
pass (1,17): 17 = a*(1)² + b*(1) +c = a+b+c ...(2)
pass (2,8): 8 = a*(2)² + b*(2) +c = 4a+2b+c ...(3)
(2)-(1): 2b = 0 b=0
(3)-(2): 8-17 = 3a + b = 3a
==> -9 = 3a a=-3
c = 17-a-b = 17 +3 - 0 = 20
equation: y = -3x² + 20
