The vertex is either the highest (if the parabola opens downward) or the lowest (if the parabola opens upward) point on the graph of the parabola. (With obvious extensions to parabolas opening in other directions.)

The vertex is always on the line of symmetry of the parabola. For up or down opening parabolas this is always the line x = -b/(2a) where the parabola is of the form y = ax^2 + bx + c. (This gives the x value so you can find the y value yourself.)

In your case you know the parabola opens upward since a > 0.

-Dan