string(274) "get document error：https://zhidao.baidu.com/search?lm=0&rn=10&pn=0&fr=search&dyTabStr=null&word=%E6%95%B0%E5%AD%A6%E4%B8%80%E5%85%83%E4%BA%8C%E6%AC%A1%E6%96%B9%E7%A8%8B%E8%A7%A3%E7%9A%84%E5%85%AC%E5%BC%8F => Failed to connect to 14.116.215.7 port 38225: Connection refused"
数学一元二次方程解的公式
