import math

def quadratic(a,b,c):

    dert=b*b-4*a*c

    if a==0:

        return -c/b

    if dert>0:

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

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

        return x2, x1

    elif dert==0:

        x1=-b/(2*a)

        return x1

    else :

        print('no answer')

        return 0




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')