import math

def quadratic_equation(a, b, c):

    de = b**2 - 4*a*c

    if de>=0:

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

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

        return x1, x2

    else:

        return

print quadratic_equation(2, 3, 0)

print quadratic_equation(1, -6, 5)