string(294) "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%E7%9A%84%E8%A7%A3%E7%9A%84%E5%85%AC%E5%BC%8F%E6%98%AF%E4%BB%80%E4%B9%88 => Failed to connect to 101.89.117.144 port 38208: Connection refused"
一元二次方程的解的公式是什么
