根据对话内容和所给汉语提示，在空白处填入单词的正确形式。每空限填一词。
Dear students,
      As we all know, good health is important for success in exams, so I’m   ____   (写) to give you all some ways which are   ____   (有帮助的) to you
       First of all, it is necessary that you sleep well    ____   (在……期间) the exam period in order that you can have  ____   (足够的) energy. Second, a healthy, balanced  ____   (饮食) is important to your success. In order to eat healthily, try to avoid eating food high in fat. It’s   ____  (更好) for you to eat a lot of vegetables and fresh fruit which are  ____  (充满) of vitamins. Besides, don’t forget to take exercise no matter how busy you are. It can help you build a strong ____    (身体) as well as making you relaxed.
 ____  (另一个) way I will share with you is this: studying with other people will help you discuss and form your own ideas. Plus, you won’t feel  ____  (孤单的)!
   Best wishes and stay healthy.
                                                                                                                                                 Yours,
                                                                                                                                                 Li Hua

已知数轴上三点M，O，N对应的数分别为﹣2，0，4，点P为数轴上任意一点，其对应的数为x．

（1）如果点P到点M、点N的距离相等，那么x的值是多少？

（2）数轴上是否存在点P，使点P到点M、点N的距离之和是7？如果存在，求出x的值；如果不存在，请说明理由；

（3）如果点P以每秒钟6个单位长度的速度从点O向右运动时，点M和点N分别以每秒钟1个单位长度和每秒钟3个单位长度的速度也向右运动，且三点同时出发，那么经过几秒钟，点P到点M、点N的距离相等．

下列各项中划线字的注音全对的一项是（    ）。

（Ⅰ）求 $f\left(x\right)$ 在 $x\in -\frac{\pi }{2},0$ 时的值域；

（Ⅱ）已知数列 $a_n=n^{2}f\left(\frac{n\pi }{2}-\frac{11\pi }{24}\right)$ $\left(n\in N^{*}\right)$ ，求 $\left\{a_n\right\}$ 的前2n项和 $S_{2n}$ ．