string(264) "get document error：https://zhidao.baidu.com/search?lm=0&rn=10&pn=0&fr=search&dyTabStr=null&word=%E4%B8%80%E5%85%83%E4%BA%8C%E6%AC%A1%E6%96%B9%E7%A8%8B%E8%A7%A3%E6%96%B9%E7%A8%8B%E6%AD%A5%E9%AA%A4 => Failed to connect to 14.18.46.51 port 38206: Connection refused"
一元二次方程解方程步骤
