Problem 9b.

     
#9b
def square(x,y,l):
 sx=(x-l/2)
 sy=(y-l/2)
 ex=(x+l/2)
 ey=(y+l/2)
 g.line (sx,sy,sx,ey)
 g.line (sx,ey,ex,ey)
 g.line (ex,ey,ex,sy)
 g.line (ex,sy,sx,sy)
 
for a in range (0,20):
 g.norefresh()
 g.pen (40-2*a)
 square (120,45,(2*((a)*(a))))
 square (120,45,(2*((a)*(a))-1))
 square (120,45,(2*((a)*(a))-2))
 g.pause (3)
 g.pause (3)
 if a>4:
  g.pen (43-2*a)
  square (170,181,(2*((a-4)*(a-4))))
  square (170,181,(2*((a-4)*(a-4)-1)))
  square (170,181,(2*((a-4)*(a-4))-2))
  if a>6:
   g.pen (45-2*a)
   square (43,164,(2*((a-6)*(a-6))))
   square (43,164,(2*((a-6)*(a-6))-1))
   square (43,164,(2*((a-6)*(a-6))-2))
 g.pause(3)
 g.pause(3)

-gary escudero