import math

def quadratic(a, b, c):
    if a == 0:
        if b == 0:
            if c == 0:
                return '恒成立';
            else :
                return None;
        else :
            return -c / b;
    elif b * b - 4 * a * c < 0:
        return '无解';
    else :
        return (-b + math.sqrt((b * b) - (4 * a * c))) / (2 * a) ,(-b - math.sqrt((b * b) - (4 * a * c))) / (2 * a);

print(quadratic(2, 3, 1)) # => (-0.5, -1.0)
print(quadratic(1, 3, -4)) # => (1.0, -4.0)
print(quadratic(0, 0, 0)) # => (-0.5, -1.0)
print(quadratic(0, 0, 1)) # => (1.0, -4.0)