we know that
the equation of a vertical parabola into vertex form is equal to

where
(h,k)-------> is the vertex of the parabola
if
-------> the parabola open upwards
if
-------> the parabola open downwards
<u>case A)</u> 
so
-------> the parabola open downwards
the vertex is the point
------> is a maximum
therefore
open downwards
<u>case B</u>) 
so
-------> the parabola open upwards
the vertex is the point
--------> is a minimum
therefore
open upwards
<u>case C</u>) 
so
-------> the parabola open upwards
the vertex is the point
--------> is a minimum
therefore
open upwards
therefore
<u>the answer is</u>
open downwards