import math

def quadratic(a, b, c):
    if b*b-4*a*c < 0:
        return ("无解")
    else:
        x1 = (-b + math.sqrt(b*b-4*a*c))/(2*a)
        x2 = (-b - math.sqrt(b*b-4*a*c))/(2*a)
        return x1,x2
print (quadratic(2, 3, 1))
print(quadratic(1, 3, -4))