Question 366794
{{{drawing(300,300,-5,6,-20,20,grid(1),blue(line(-4,-100,-4,100)),circle(0,16,0.05),
circle(0,16,0.15),
circle(0,16,0.25),
circle(0,16,0.2),
circle(0,16,0.1),
blue(line(-100,16,100,16)),
blue(line(5,100,5,-100)),graph(300,300,-5,6,-20,20,0,16-x^2))}}}