In this problem
we have a vertical parabola open downward
so
the vertex is a maximum
Looking at the graph
The vertex is the point (0,4)
The axis of symmetry is x=0 (y-axis)
The zeros are x=-2 and x=2
The domain is all real numbers -----> interval (-infinity, infinity)
The range is all real numbers less than or equal to 4 ----> interval (-infinity,4]