string(276) "get document error：https://zhidao.baidu.com/search?lm=0&rn=10&pn=0&fr=search&dyTabStr=null&word=%E7%9B%88%E4%BA%8F%E5%B9%B3%E8%A1%A1%E7%82%B9%E8%AE%A1%E7%AE%97%E4%BE%8B%E9%A2%98%E5%8F%8A%E7%AD%94%E6%A1%88 => Failed to connect to 101.89.143.195 port 38205: Connection refused"
盈亏平衡点计算例题及答案
