Let y=-16x2+40x+50,
y=50-16(x2-5x/2+25/16-25/16),
y=50-16((x-5/4)2-25/16),
y=50-16(x-5/4)2+25,
y=75-16(x-5/4)2.
The axis of symmetry is x=5/4=1.25, a vertical line (parallel to the y-axis), not a single point.
The single point is in fact the vertex of the parabola at (1.25,75).