If $$y = ax^2 + bx + c$$, $$a \ne 0$$, then $$y = a\left(x + \frac{b}{2a}\right)^2 + \frac{4ac - b^2}{4a}$$

A

If $$a$$ is positive then minimum value of $$y$$ is $$\frac{4ac - b^2}{4a}$$

B

If $$a$$ is positive then maximum value of $$y$$ is $$\frac{4ac - b^2}{4a}$$

C

If $$a$$ is negative then minimum value of $$y$$ is $$\frac{4ac - b^2}{4a}$$

D

If $$a$$ is negative then maximum value of $$y$$ is $$\frac{4ac - b^2}{4a}$$