When a> 0, the parable has an upward concavity and a minimum point V; when <0, the parable has downward concavity and a maximum point V.
In any case, the coordinates of V are . See the graphics:
The image set Im of the function y = ax2 + bx + c, a 0 is the set of values y can assume. There are two possibilities:
1st - when a> 0,
2nd when a <0,
Next: Parable Construction