y = ax² + bx + c

0 = a(2)² + 2b + c

0 = 4a + 2b + c

c = - 4a - 2b

y = ax² + bx + c

0 = a(-4)² - 4b + c

0 = 16a - 4b + c

c = - 16a + 4b

c = c

- 4a - 2b = - 16a + 4b

- 4a + 16a = 4b + 2b

12a = 6b

b = 2a

y = ax² + bx + c

- 4 = a(0)² + b(0) + c

c = - 4

y = ax² + bx + c

0 = a(2)² + 2a(2) - 4

4 = 4a + 4a

8a = 4

a = 1/2

b = 2a

b = 2(1/2)

b = 1

y = ax² + bx + c

y = x²/2 + x - 4

/\ = b² - 4ac

/\ = 1 - 4(1/2)(-4)

/\ = 1 + 8

/\ = 9

x = - b / 2a

x = - 1 / 2(1/2)

x = - 1 / 1

x = - 1

y = - /\ / 4a

y = - 9 / 4(1/2)

y = - 9 / 2

------------------------- > ( - 1 , - 9/2 )