用Python實現解一元二次方程，來自廖雪峰Pyhton3.0教程課後習題

# -*- coding: utf-8 -*-

import math

def quadratic(a, b, c):
    if (b * b - 4 * a * c) < 0:
        return 'None'
    Delte = math.sqrt(b * b - 4 * a * c)
    if Delte > 0:
        x = (- b + Delte) / (2 * a)
        y = (- b - Delte) / (2 * a)
        return
 
 x, y
    else:
        x = (- b) / (2 * a)
        return x

# 測試:
print(quadratic(2, 3, 1)) # => (-0.5, -1.0)
print(quadratic(1, 3, -4)) # => (1.0, -4.0)