import  math

def quadratic(a, b, c):
    if b * b - 4 * a * c > 0: # 该方程有2个解
        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
    elif b * b - 4 * a * c == 0: # 只有一个解
        x = (-b + math.sqrt(b * b - 4 * a * c)) / (2 * a)
        return x
    else:
        return '此方程无解'

def check_abc(a,b,c):

    m =''
    m2 = ''
    m3 = ''

    if not isinstance(a,(int,float)):
        m = '\'%s\'不是数字' % a
    elif a==0:
        return '此方程无意义'

    if not isinstance(b,(int,float)):
        m2 = '\n\'%s\'不是数字' % b

    if not isinstance(c,(int,float)):
        m3 = '\n\'%s\'不是数字' % c

    if len(m+m2+m3)>0:
        return a,b,c,m+m2+m3
    else:
        return True

def operation_abc(a,b,c):
  if isinstance(check_abc(a,b,c),bool):
      return quadratic(a,b,c)
  else:
      return '一元二次方程：%sx^2 + %sx + %s = 0,%s'% (check_abc(a,b,c)[0],check_abc(a,b,c)[1],check_abc(a,b,c)[2],check_abc(a,b,c)[3])

a = input('一元二次方程：ax^2 + bx + c = 0,请输入 a :')
while not  a.isdigit():
    a = input('请输入数字 a :')

b = input('一元二次方程：ax^2 + bx + c = 0,请输入 b :')
while not  b.isdigit():
    b = input('请输入数字 b :')

c = input('一元二次方程：ax^2 + bx + c = 0,请输入 c :')
while not  c.isdigit():
    c = input('请输入数字 c :')

print(operation_abc(float(a),float(b),float(c)))