delta=b*b-4*a*c

 if delta > 0:

   x1=(-b+math.sqrt(delta))/(2*a)

   x2=(-b-math.sqrt(delta))/(2*a)

   return x1,x2

   print('有实根',x1,x2)

 elif delta == 0:

   x1=(-b)/2*a

   return x1

   print(x1)

 elif delta < 0:

   return None

   print('无实根')