import math

def quadratic(a, b, c):

    t = (b*b-4*a*c)

    if t<0:

        return

    elif t>0:

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

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

        return x1,x2

    else:

        return ((-b) + math.sqrt(t)) / (2*a)

print('quadratic(2, 3, 1) =', quadratic(2, 3, 1))

print('quadratic(1, 3, -4) =', quadratic(1, 3, -4))

if quadratic(2, 3, 1) != (-0.5, -1.0):

    print('测试失败')

elif quadratic(1, 3, -4) != (1.0, -4.0):

    print('测试失败')

else:

    print('测试成功')