# -*- coding: utf-8 -*-
import math

def quadratic_equation(a, b, c):
??? if b*b-4*a*c>=0:
??????? x=(-b+math.sqrt(b*b-4*a*c))/a/2
??????? y=(-b-math.sqrt(b*b-4*a*c))/a/2
??????? return x,y
??? else:
??????? return u'不存在'
print quadratic_equation(2, 3, 0)
print quadratic_equation(1, -6, 5)
print quadratic_equation(10, -6, 5)