import math def quadratic_equation(a, b, c):    de=b*b-4*a*c    if a!=0|de>=0:        x=(-b+math.sqrt(de))/(2*a)        y=(-b-math.sqrt(de))/(2*a)        return x,y    else:        return none print quadratic_equation(2, 3, 0) print quadratic_equation(1, -6, 5) 为什么不通过啊啊