Respuesta :

The equation of a parabola is:
[tex]y = ax {}^{2} + bx + c[/tex]
If a>0, then the parabola opens up;
If a<0, then the parabola opens down.
The coordinates of focus are:
[tex]( - \frac{b}{2a} \: \: \frac{1 - b {}^{2} + 4ac}{4a} )[/tex]