Let's go through first form of the parabola.
f ( x ) = a ( x - h )2 + k
There are two pieces of information regarding the parabola which we can instantly get from this function. First, if a is +ve then the parabola will open up and if a is +ve then the parabola will open down. Second, the vertex of the parabola is the point ( h, k ) . Be very careful with signs while getting the vertex here.
So, while we are lucky sufficient to have this form of the parabola we are given the vertex for free.