古人说：“以铜为镜，可以正衣冠；以古为镜，可以知兴替；以人为镜，可以明得失。”结合课文和你所知道的事例，谈谈你对这句话的理解。

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    Things can become very dangerous in a fire. 1 will you do if you cannot get out of the room?

    If you cannot get out of the room, close the door and put blankets (毛毯) at the 2 of the door. They can 3 the smoke from coming in.

    And 4 119 for help. Then open the window and 5 for help. Wave (摇摆) a piece of cloth from the window. Let people know that you are still inside the room.

    Don't stay under the bed or in the wardrobe. When the firefighters come in, they will have to 6 you. So stay by the window.

    If your clothes 7 fire, remember the words: stop, drop and roll.

    Stop running. Moving around will make the fire even 8. Drop and lie down on the floor. Roll around, from one side to 9 to stop the fire.

    If your friend's clothes are on fire, don't let him or her 10. Shout, "Stop, drop and roll!" When he or she is rolling on the floor, you can use a blanket or other heavy cloth to help to put out the fire on his or her clothes.

计算：2008²﹣2007×2009=____，已知a+$\frac{1}{a}$=3，则$a^2+\frac{1}{a^2}$=____．

定义：a是不为1的有理数，我们把 $\frac{1}{1-a}$ 称为a的差倒数．

如：2的差倒数是 $\frac{1}{1-2}=-1$ ，﹣1的差倒数是 $\frac{1}{1-\left(-1\right)}$ = $\frac{1}{2}$ ．

已知 $a_1=-\frac{1}{3}$ ，