### [娱乐] 一个监控NIKE官网NBA球衣打折的QQ机器人

• Windows服务器一台，阿里云ECS即可（Linux也可以但是需要Wine，不如直接原生Windows）
• QQ小号一个，用来作为发送消息的载体

### JetBrains Quest 免费领取三个月全家桶 解密

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Have you seen the source code of the JetBrains website?


      O
{o)xxx|===============-
O

Welcome to the JetBrains Quest.

What awaits ahead is a series of challenges. Each one will require a little initiative, a little thinking, and a whole lot of JetBrains to get to the end. Cheating is allowed and in some places encouraged. You have until the 15th of March at 12:00 CET to finish all the quests.
Getting to the end of each quest will earn you a reward.
Let the quest commence!

JetBrains has a lot of products, but there is one that looks like a joke on our Products page, you should start there... (hint: use Chrome Incognito mode)
It’s dangerous to go alone take this key: Good luck! == Jrrg#oxfn$O -===============|xxx(o} O  看到了hint说使用Chrome的无痕模式，那我们无痕模式打开一下Products 页面。顺便，注意他的一句话：带上这个key Good luck! == Jrrg#oxfn$

## 1. 回顾高等数学：多元数量函数的梯度

$$\nabla f_{\boldsymbol{x}} \overset{\underset{\mathrm{def}}{}}{=} \left[ \frac{\partial f }{\partial x_1}, \frac{\partial f }{\partial x_2},\cdots,\frac{\partial f }{\partial x_n} \right]=\frac{\partial f }{\partial \boldsymbol{x}}$$

\begin{aligned} df &= \frac{\partial f}{\partial x_1}dx_1+\frac{\partial f}{\partial x_2}dx_2+\cdots+\frac{\partial f}{\partial x_n}dx_n \\ &=\left[ \frac{\partial f }{\partial x_1}, \frac{\partial f }{\partial x_2},\cdots,\frac{\partial f }{\partial x_n} \right] \left[dx_1, dx_2,\cdots,dx_n \right]^T \\ &=\frac{\partial f }{\partial \boldsymbol{x}} d\boldsymbol{x} \end{aligned}

### 2019 kali 笔记本电脑 双系统 双显卡 配置nvidia显卡支持外接hdmi显示器

。。。绝大多数人都会照着官方的教程做，但是这个操作是针对只有一张nvidia显卡的台式机来说的，而不是笔记本的双显卡。。。。按照这个教程，装完之后是可以用这个gpu做运算的，但是不能用来做显示。。。插上外接显示器没有任何反应，用xrandr根本检测不到有外界显示器存在。

Linux 5.3.0-kali2-amd64 #1 SMP Debian 5.3.9-3kali1 (2019-11-20) x86_64 GNU/Linux