您可以通过发表评论的方式提问题, 我如果有时间就会思考, 并给出答案的链接.
如果您学过Latex, 发表评论的时候请直接输入Latex公式; 反之, 请直接上传图片 (扫描、拍照、mathtype编辑), 发表评论的最后一个按钮 
即可实现.
另外, 如果是书上的题目, 请给出哪本书; 如果是哪个学校的考研题, 也请注明是哪个学校哪年的, 并请通过邮件 zhangzujin361@163.com 发给我试题. 其他情形就不要发表评论了.
评论1与评论2已经给出了示例.
You may just post a question in this webpage, and I shall think about it if I have time, and I will link the answer to it.
If you know Latex, you may just type it in latex form (after doing this, just click 
);
otherwise, you may just upload the picture (have you seen the last icon in posting a comment? Just click it and upload your png,jpg or gif files which are generated by mathtype software or others).
I would be very appreciated if you point out the references you are doing.
Good luck then.
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原文：http://www.cnblogs.com/zhangzujin/p/3836319.html