表达式求值，四舍五入保留两位

from decimal import Decimal
try:
    a = float(input())
    b = float(input())
    c = float(input())
    x = Decimal((-1*b+(b**2-4*a*c)**0.5)/(2*a)).quantize(Decimal('0.01'), rounding='ROUND_HALF_UP')
    print(x)
except Exception as e:
    print(e)