Python好难啊，求哪位可以写一下，求解。

#!/usr/bin/python
# -*- coding: UTF-8 -*-
"""
@author: Roc-xb
"""

import math


def quadratic(a, b, c):
    key = b ** 2 - 4 * a * c
    if key > 0:
        x1 = (-b + math.sqrt(key)) / 2 * a
        x2 = (-b - math.sqrt(key)) / 2 * a
    if key == 0:
        x1 = -b / 2 * a
        x2 = x1
    if key < 0:
        print('方程无解')
        return (None, None)
    return ("{:.2f}".format(x1), "{:.2f}".format(x2))


if __name__ == '__main__':
    print(quadratic(1, 4, 2))