http://ddia.vonng.com/#/ch9?id=%E4%B8%80%E8%87%B4%E6%80%A7%E4%BF%9D%E8%AF%81:~:text=%E3%80%82-,%E5%A6%82%E6%9E%9C,-x%E2%89%A0v_%7Bold 出现两个x=V old