import math

def quadratic(a,b,c):

    if not isinstance(a,(int,float)):

        raise TypeError('数据类型错误')

    if not isinstance(b,(int,float)):

        raise TypeError('数据类型错误')

    if not isinstance(c,(int,float)):

        raise TypeError('数据类型错误')

    if b**2-4*a*c >= 0:

        x1 = (-b + math.sqrt(b**2-4*a*c))/(2*a)

        x2 = (-b - math.sqrt(b**2-4*a*c))/(2*a)

        if b**2-4*a*c == 0:

            print('x1=x2=%.2f'%x1)

        else:

            print('x1=%.2f'%x1,'x2=%.2f'%x2)

    else:

        print('不存在实根')

quadratic(3,5,1)