
可能为负值
<img src="https://attachment.cnbkw.com/bkwimg/up/202002/021249c1c5a52beb4ac4b68c92f5b58ef40a.png" alt=""><img src="https://attachment.cnbkw.com/bkwimg/up/202002/02123227c7bddef7479e812daa43f1ebec48.png" alt="">
<span style="">随着解释变量的增多,
<span style="">的值可能变小,甚至可能为负值。