#!/usr/bin/env python

# -*- encoding: utf-8 -*-

import math

def quadratic(a,b,c):

    if not isinstance(a+b+c,(int,float)):

        raise TypeError('请输入数字！')

    if a == 0 :

        x = -b/c

        return x

    delta = b**2-4*a*c

    if delta > 0:

        x1 = (-b + math.sqrt(delta)) / (2 * a)

        x2 = (-b - math.sqrt(delta)) / (2 * a)

        return x1,x2

    elif delta == 0:

         x = -b/2*a

    elif delta < 0:

        print('无实数解')

print('quadratic(2, 3, 1) =', quadratic(2, 3, 1))

print('quadratic(1, 3, -4) =', quadratic(1, 3, -4))

if quadratic(2, 3, 1) != (-0.5, -1.0):

    print('测试失败')

elif quadratic(1, 3, -4) != (1.0, -4.0):

    print('测试失败')

else:

    print('测试成功')