import math

def quadratic_equation(a, b, c):
    det=b*b-4*a*c
    if det<0:
        return none
    elif det==0:
        return -b/(a*2)
    else:
        return (-b-math.sqrt(det))/(2*a),(-b+math.sqrt(det))/2/a
print quadratic_equation(2, 3, 0)
print quadratic_equation(1, -6, 5)