增加：在缺词处加一个漏字符号（∧），并在其下面写出该加的词。

删除：把多余的词用斜线（\）划掉。

修改：在错的词下划一横线，并在该词下面写出修改后的词。

注意：1.每处错误及其修改均仅限一词；2.只允许修改10处，多者（从第11处起）不计分。

    An opening week held in our school last week so that we could show a great achievements we made in art education.

    The art works exhibition went on from Monday to Friday, exhibit the excellent art works, such as paper cuts, paintings and flower arrangements. Both of the art works were created by the students of our school. That attracted the public most was the singing and dancing performances in Friday afternoon. All these activities draw the close attention of the public and parents as well, receiving high praises from the public.

    Through these activity, the public has a better understanding of our school. As a result of ,we all think that the opening week was of great successful.

观察下列等式： 1²=1,1²-2²=-3,  1²-2²+3²=6，1²-2²+3²-4²=-10  ，由以上等式推测出一个一般性的结论：

对于$n\in N^{*},1^2-2^2+3^2-4^2+..+(-1{)}^{n+1}{n}^2=$  ____.

已知全集U=N，集合$P=\{1,2,3,4,6\},P=\{1,2,3,5,9\}$则$P\cap \left(C_{U}Q\right)=$(    )

如图，△ABC的中线BD、CE交于点O，连接OA，点G、F分别为OC、OB的中点，BC=8，AO=6，则四边形DEFG的周长为（　　）