markdown公式编辑参考
markdown编辑数学公式 http://blog.csdn.net/lk7688535/article/details/52528307
https://math.meta.stackexchange.com/questions/5020/mathjax-basic-tutorial-and-quick-reference
markdown编辑数学公式 http://blog.csdn.net/lk7688535/article/details/52528307
https://math.meta.stackexchange.com/questions/5020/mathjax-basic-tutorial-and-quick-reference
