The equation of a parabola takes the form
where (h, k) represents the vertex of the graphed equation and a impacts how "fat" or "skinny" the parabola is (or whether it opens up or down).
A parabola with the equation
looks like:
Note in this case h and k are equal to 0 and a is equal to 1.
The question (& answer) were taken from p. 731 of the Discover Science Almanac. The book was published by Hyperion in 2003.