python求解ax² + bx + c = 0

系数需满足条件：

• a,b不能同时为0
• b²-4ac≠0
  
  

代码如下
def quadratic(a, b, c):
    """
    返回ax² + bx + c = 0的
    """
    if not all(map(lambda x: isinstance(x, (int, float)), (a, b, c))):
        raise TypeError('参数类型只能为int, float')
    if a == 0 and b == 0:
        return None # a, b不能同时为0
    elif a == 0 and b != 0:
        return c / b 
    elif a != 0 and b == 0:
        return math.sqrt(c / a)
    else:
        d = b**2 - 4*a*c
        if d <0 :
            return None # b²-4ac不能为0
        else:
            return (-b + math.sqrt(d)) / 2*a, (-b - math.sqrt(d)) / 2*a